Note: Descriptions are shown in the official language in which they were submitted.
98~L5
BACKGROUND OF THE INV~5NTION
I. FIELD OF THE_INVENTION
The present invention relates to a process for
wrapping bundles with stretched film web and more
particularly, a process of unitizing a bundle having a
plurality of bundle units at extremely high throughput
rates with high film web elongation and containment force
on the bundles.
II . DESCRIPTION OF THE RELATED ART
_
It has become popular to package products into bundles
by wrapping the products with a web of stretched plastic
film. The elasticity of the stretched plastic film holds
the products of the bundle under tension while unitizing
and covering the bundle.
For a film web wrapping process to be commercially
competitive, it has been increasingly necessary to wrap
bundles at a very high throughput. This is especially
true for business enterprises which need to wrap large
numbers of bundles having a uniform cross-sectional shape.
The conventional cross-sectional shape is rectangular in
order to economize shipping space and facilitate
stacking. Due to corner variations which change the
effective wrapping radius, bundles having such rectangular
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cross-secti.ons or other non-circular cross-sections, present a
fluctuation in its demand for ~.ilm web as the film web is
wrapped around its periphery.
To enable the background to the invention to be described
with the aid of diagrams, the figures of the drawings will
first be listed.
Figure l is a perspective view of a dual-stage wrapping
apparatus capable of performing the process of the present
invention;
Figure 2 is a side view of the apparatus of Figure 1;
Figure 3 is a front cutaway view taken along line 3-3' of
Figure 2;
Figure 4 is a rear cutaway view taken along line 4-4' of
Figure 3;
Figure 5 i5 2 graph of demand for film web at a wrapped
rectangular applicator mandrel of the present invention;
Figure 6 is a graph of film web supply from the dispenser
of the present invention;
Figure 7 is a graph of film web elongation exerted
between the dispenser and the applicator mandrel of the
present invention; based on the demand shown in Fig. 5 and the
~upply shown in Fig. 6;
Figure a is a graph illustrating the relationship of force
and elon~ation in conventional wrapping procecsex;
Pigure 9 is a schematic view of a conventional wrapping con-
veyor and bundle;
Figure lO is a schematic view of a prior art dispenser and
bundle, illustrating a point of minimum demand for film web at
the bundle;
Figure ll is the schematic view of the bundle and dispenser
at Fig. lO at a later point in time, illustrating a point of max-
imum demand for film web at the bundle;
Figure 12 is a schematic view of a dispenser apparatus and
bundle of Fig. ll at a later point in time, illustrating a point
of secondary minimum demand for film web at the bundle;
Figure 13 is an isolated side view of an elongation mecha-
nism of the apparatus of Figure 3;
Figure 14 is a graph illustrating the relationship of stress
and strain on the film web when pre-stretched in the film web
dispenser and stretched again at the applicator mandrel of the
presen~ invention
Figure lS is a ~raph illustrating the relationship of stress
' and strain on film web stretched between the dispenser and the
applicator mandrel of the present inven~ion;
Figure 16 is a schematic view of a bundle and an applicator
mandrel ~panning the full width of widest bundle surfaces;
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Figure 17 is a schematic view of a bundle and an applicator
mandrel spanning a portion of the width of opposed widest bundle
surfaces;
~ igure 18 is a schematic side view illustrating severance of
continuously wrapped bundles;
Figure 19 is an isolated side view, upstream from the first
wrapping stage, of an applicator mandrel configured for tall bun~
dle contours;
Figure 20 is an isolated side view, downstream from the sec-
ond wrapping stage, of the applicator mandrel of Figure 19;
Figure 21 is a front view of the applicator mandrel of Fig-
ure 19
Figure 22 is an isolated perspective view of a transmission
for the wrapping conveyor of Figure 2.
Figure 23 is a gr~ph of demand for film web:
Figure 24 is à graph of film web supply from the dispenser;
Figure 25 is a graph of film web elongation under the demand
shown in Fig. 23 and the supply shown in Fig 2~; and
Figure 26 is a diagram o~ a motor speed controller with re-
2~ generative capabilities which are arranged according to the pres-
; ent invention,
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General Background to Problems With Varying
Demand Rates Durinq Wrappinq
Figs. 10-12 show the fluctuation in film demand due to bundle
shape variations such as corners. A bundle 40 is centered on axis Y.
A film web dispenser 70 is revolved around axis Y at a constant
angular velocity and at a constant distance from axis Y to wrap film
web 58, moving in direction D around stationary bundle 40. The
effective wrapping radius increases from A to B during the
progression between Figs. lo and 11 and decreases to radius c between
Figs. 11 and 12. The effective wrapping radii A, B, and C extend
between center of revolution Y and tangent T, and if rotated, form
circles J, X, and L, respectively.
Under constant angular velocity of film web dispenser 70, the
film web demand rate is proportional to the effective wrapping
radius. Fig. lO shows a minimum demand rate where the wider
side of an oblong bundle has just been wrapped. Fig. 11 shows
a maximum demand rate where the film engages a corner. Fig. 12
shows a secondary minimum demand rate where the narrower side
of an oblong bundle has just been wrapped. I'his secondary
minimum demand rate is less than the maximum demand rate shown
in Fig. 11, but greater than the minimum demand rate shown in Fig.
s
lO because effective radius C is greate~ than effective radius A
due to the oblong shape of the bundle.
The relation between demand rate or speed and time is shown
in Fig. S. The maximum demand rate or speed existing at the cor-
ners in the condition shown in Fig. ll is indicated by maximum
points 154 in Fig. 5. Minimum demand rates or speeds in the
positions shown in Figs. lO and 12 are indicated ~y minimum
points 1S2 in Fig. 5.
If f;lm web 58 is dicpensed from film web dispenser 70 at a
constant supply rate such as that s~own in Fiy. 6, the film web
stretched between film web dispenser 70 and bundle ~0 would fol-
low a pattern of elongation over time that would be similar to
the pattern of the demand rate over time. Such a pattern of
elongation over time is shown in Fi~. 7. This elongation pattern
of Fig. 7 is similar to the demand rate pattern shown in Fig. 5.
Elongation maximums 144 correspond to demand rate maximums 15
Elongation minimums 142 correspond to demand rate minimums 152.
During wrapping, bundle edges isolate tension on each film
web segment applied to a bundle surface from film web segments
applied to adjacent surfaces. The effec~ive con~ainment force on
the bundle is locked in just as it covers a bundle surface in the
positions shown in Figs. la and 120 Therefore, the locking in of
containment ~orce occurs where the demand rate and force on the
film is lowest in the wrappin~ cycle.
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It can be appreciated that irl the arran~ement shown in Figs.
10-12, when the bundle is off-center relative to rotation axis Y,
the demand rate and wrap forces would fluctuate even more widely
between a maximum and a minimum for each side of the bundle due
to greater variations in the effecti~e wrapping radius.
Within the context of this varying demand rate due to bun-
dles with a non-circular cross-section, efforts were made to con~
trol the rate at which the film web is dispensed ~rom the film
web dispenser to provide a sufficient containment force due to
stressed film web on the wrapped bundle while preventing film
rupture at excessively high stresses. A varying film web demand
rate creates the adverse situation that the film stress-strain
maximum must not rupture the film, while the stress-strain mini-
mum is the containment force locked in after wrapping. In order
to have any containment force, the minimum must exceed zero
stressO
Demand Force Controlled SU~1Y Rate SYstems
At slow film web supply rates, the force on the film web be-
tween the film we~ dispenser and t}le bundle generally proportion-
al to the varying demand rate. Therefore, early film web dis-
pensers controlled the supply rate of the film web by measuring
the force on the film web. Then they varied the film web supply
rate of the dispenser accordingly so that the s~pply rate of the
film web from the dispenser followed the demand rate for the film
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web caused by the corner variations of the bundle. By maintain-
ing a constant force on the film web, the stress-strain values
for the film web could be kept constant over tirne and therefore
maintain a high containment force while pre~enting an increase in
force due to fluctuations in demand rate which would rupture the
film~ The demand, supply, and force curves of this control
arrangement are seen in Figs. 23, 24 and 25.
However, there are major drawbacks in controlling film web
dispenser supply rates by the sensing of variations in force on a
film web due to the varying demand rate of a non-circular cross-
sectioned bundle. The first drawback is that any imperfection
such as a hole in the film web reduces the area over which the
force is applied. This dramatically increases the stress on the
remaining cross-sectional area of the film web. The hole is fur-
ther elongated and enlarged because the control system automat-
ically decreases the supply speed at the dispenser~ This growing
difference between the supply and demand speeds finally ruptures
the film.
The second drawback occurs when the film web is dispensed at
higher speeds in an attempt to increase throughput. The inertia
of the film dispenser and the elasticity of the film web between
the film web dispenser and the bundle cause a phase delay or lag
in supply speed changes relative to demand speed changes. This
phase delay has its worst drawbacks when the supply rate lags the
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demand rate such that the supply rate is increasing while the de-
mand rate is decreasing and the supply rate is decreasing while
the demand rate is increasing. Rather than equalizing the force
on the film over time due to the variations in demand rate, such
a phase delay causes a heightened variation in force and elonga-
tion on the film web, thereby rupturing the film web.
S~eed Contro_led SupPlY Rate Systems
A second type of control for varying the supply rate o~ the
film dispenser due to the variations in demand rate was developed
in order to overcome the drawbacks of the force controlled
dispensing system This system, rather than sensing force in the
web, was designed to vary the supply rate of tne film web
according to the known supply rate which would be required to
meet the instantaneous demand rate at each position of the film
web dispenser's revolution about the bundle. ~y not sensing
force, the film web was not ruptured due to the drawbacks caused
by its imperfections. In addition, phase delay drawbacks were
avoided at somewhat higher speeds. However, as the speed of the
film web dispenser was further increased, an inordinate amount of
power was required in order to more quickly accelerate and
deaccelerate the f;lm web supplied from the film web dispenser.
Therefore, film web dispensers which controlled supply rate
according to dispenser position were unable to attain high film
web supply speeds as well.
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Stress-Strain Characteristics of Pilm_Webs
As shown in Fig. 8, filrn webs exhibit a stress-strain curve
having a steep initial linear portion l~OE where elastic behavior
is present and a gradual second linear portion 140P where plastic
behavior is present. In between these two linear ranges is an
intermediate range or region on the stress-strain curve commonly
known as the yield point 141. It is in the range of this yield
point that the stress-strain ~ehavior of the film web changes be-
tween substantially elastic to plastic. Film webs stretched
above yield point gain significantly in modulus and ultimate
strength. For instance, a low density polyethylene film web will
increase its ultimate strength in pounds per square inch of
cross-sectional area by 300% after being elongated approximately
300~. Therefare, current stretch wrapping operations use pre-
stretch subsystems in the film web dispenser as a matter of
course.
Stress-strain curves are dependent upon the end conditions
of the film web and the previous history of stress and strain in
the film web. For example, in the arrangement shown in Fig~ 10,
the stress-strain curve of ~he film web between closely spaced
rollers a and b in the pre-stretch subsystem of the film web dis-
penser 70 is different although generally similar in shape to the
stress-strain curve of the film web between the more greatly
spaced downstream roller b and bundle 40.
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If an uns~retched film web is stretched from the point of
or;gin 0 along the elastic portion l~OE o the stress-strain
curve to a point no further than yield point 141, the film web
will return to a stress-strain condition along the same
curve 140E when the stretch force is reduced or removed, and
will once again have zero strain at zero force.
However, if the film web is stretched beyond yield point 141
so that it reaches a point on the plastic portion 140P of the
curve such as point 148, the film web behavior after the force is
reduced or removed will be to progress down curve 150 rather than
returning back ~long curve 140P and 140E. If the force is now
totally removed, the film web will exhibit a permanent positive
elongation indicated by point 160.
Prestretch Devices
. _
In seeking to decrease the amount of film web needed for a
given containment force, pre-stretch devices were developed to
pre-stretch the film web in the film web dispenser under con-
trolled conditions between closely-spaced rollers which rotated
at a constant ratio. Such pre-stretching produced a permanently
elongated film with good strength characteristics. A~ shown in
Fig. 10, film web dispenser .70 includes a pre-stretch system
having upstream roller a and downstream roller b which isolate
the film web from the demand rate variances generated by the bun-
dle. Upstream roller a is conventionally connected to downstream
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798~S
roller b by a constant ratio gear train with a mechanical advan-
tage which causes downstream roLler b to rotate faster than up-
stream roller a and thereby stretch the film web between rollers
a and b.
However, conventional attempts to increase the force on the
film between the film web dispenser and the bundle resulted in
breaking the film weh. Therefore, in order to avoid rupturing
the film web after pre-stretching it in the film web dispenser,
it has been conventional to supply the film web from the dis-
10 penser to the bundle at a supply rate greater than the maximumdemand rate at the bundle so that the film web recovers or re-
duces its elongation to a value less than the elongation provided
by the pre-stretch device in the supply direction~ In addition,
the wrap orce, or force on the film web between the film web
dispenser and the bundle, is conventionally maintained at a value
less than the pre stretch force, or force on the film web between
the rollers in the pre-stretch device of the film web dispenser.
Under such conditions, the film web would elastically recover to
a point along recovery curve 150 after be;ng pre-stretched to
20 p~int 148. Therefore, the wrap force on the film web between the
film web dispenser and the bundle conventionally varied between a
minimum 1~2 and a maximum 143 on recovery curve 150 due to fluc-
tuation in demand rate caused by a non-circular bundle.
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In order to keep the film web between the film web dispenser
_ and the bundle at a stress-strain condikion along recovery
curve 150, a number o syste~s have been developed which use a
motor which supplied a positive torque to downstream roller b of
the pre-stretch device. The motor had the effect of driving the
film forward from the film web dispenser. Such motors and their
control systems have had the capability of controlling the mini-
mum film web supply speed by increasing supply speed if it were
to fall below a predetermined minimum supply rate. However, they
a have not had ~he capability of controlling the maximum film web
supply speed because it was not thought to ~e nece~sary. With
such motors and control systems, if high supply speeds were
attempted, the motors would be driven by'th'e film faster than
their set maximum constant supply speed. This set up an overrun
condition, described below, which destroyed the film web.
Therefore, even though the pre-stretch approach achieved
more precise and effective elonqation performance than rudimenta-
ry braking deYices which were originally used to stretch the
film, and although greater film web economies and improved con-
tainment reliability was increased by reducing high forces to ~hebundle, the throughput and usefulness of the pre-stretch' approach
has also been limited by the variation and forces caused by the
contours of a non-circular bundle cross-section.
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Film Speed Limited: Drawbacks o~ Other Conventional
Demand ForcQControlled_SUPPlY~RcltQ Systems ~ _ _
U.S. Patent Nos. 4,30~,920 and 4,317,322 disclose pre-
stretch dispensers in which changes in the demand rate due to
corner variations of a non-circular load are transmitted directly
through the film to the dispenser to vary the dispenser supply
rate according to the bundle demand rate. U.S. Patent Nos.
4,3~7,548, ~,387,552 and ~,524,568 disclose the use of constant
positive torque supply motors which drive the film web forward to
reduce the force and elongation on the film web between the dis-
penser and the bundle after it has been pre-stretched. U.S. Pat-
ent ~05 . ~, 503,658 and 4,514,955 disclose the use of varying pos-
itive torque supply motors which drive the film web forward to
reduce and unify over time the force and elongation on the film
web between the dispenser and the bundle after it has been pre-
stretched. However, all these systems are inoperable at high
speed throughput such as film web dispenser angular orbit
velocities above around 25 revolutions per minute. This limita-
tion is due to th~ drawbacks of demand force controlled supply
2a systems including destruction of ~ilm web due to imperfections
and phase shift effects.
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Film Force Li~ited: Drawbacks o Other Conventional
Speed Controlled Su~P-ly-Rate Syste~ms _ _
- U.S. Patent No. 4,41~,51~ discloses the use of a constant
positive speed control motor which drives the downstream roller
of the film dispenser at a supply rate in excess of the demand
rate for the ~ilm by the bundle. ~his system avoids the draw-
backs of the orce demand controlled supply systems of web hole
expansion and phase lag. However, if the film web were stretched
at a sufficiently high force and elongation rate, the motor,
rather than positively driving the film web forward, would need
to restrain the film web. Since no provision exists in conven-
tional motor system and their control systems to prevent the
motor from exceeding its set predetermined supply speed, if it is
so drawn by the film web, the internal inerta and friction of the
motor w~uld be acting in an uncontrolled way as a brake on the
film web.
Rather than driving the film web forward, the motor supply
speed would be overrun by a film web speed that was faster than
the set constant supply ~peed of the motor. The motor would be
2a driven by ~he tension in the film web between the dispenser and
the bundle in a demand force controlled way which varies the sup-
ply speed of the dispenser in response to varying the demand
speed o~ the bundle.
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~ n effect, the control of the dispenser supply rate would be
converted to a demand force controlled supply rate system with
the attendant problems of such systems/ namely destruction of
film web due to imperfections and phase lag which prevent opera-
tion at high throughput speeds.
Such overrunning of the positive speed ~upply motor would
occur at stress~strain conditions above yield point of the film
web between the dispenser and the bundle. Therefore, this would
prevent a conventional system from operating at such
stress-strain conditions above yield point.
One can tell when the motor is being driven by the film web
rather than driving the film web as intended by convention sys-
tems by analyzing whether a system is being overrun.
If higher than conventional wrap forces were attempted in a
positive torque supply motor control pre-stretch system, the film
web alone would drive the rollers of the pre-stretch system and
the positive torque motor would be driven by the pre-stretch sys-
tem at speeds higher and more vary;ng than the intended motor
speed~ The film web overdrives the motor and causes it to act in
20 an uncontrolled way as a brake when the wrap force F2, between
the film web dispenser and the bundle, is related to the pre-
stre~ch force Fl between the pre-stretch rollers according to the
following relationship:
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F2 ~ Fl* ~1 - Rs/RL)
where Rs is the radius of the downstream roller gear and RL is
the radius of the upstream roller gear. In order to have pre-
stretch, Rs is always less than RL so that the term (l - RS/RL)
is always positive and less than l, and an overrun force F2 is
less than Fl. For example, if RS/RL = lJ3, a conventional value,
then F2 equals 2/3* Fl when overrun occurs.
In summary, when overrun occurs, the supply rate of the film
web from the film web dispenser is dependent on the force of the
film web between ~he f ilm web dispenser and the bundle. Such a
system suffers from the drawbacks of force controlled dispensers
discussed above, namely, rupture of films with imperfections and
problems with phase lag which prevent high throughput operation.
~Film Force Limited: By Grossnes
of_Load and Polnt Force From Load
The Kaufman Company Stretch Command III pre-stretch pallet
load wrapping system also used a constant positive speed control
motor on the film web dispenser~ Although the pallet was rotated
at a constant angular velocity, corner variations caused a vary-
20 ing demand rate which varied over a very wide range due to the
great size of the pallet~ The film web supply speed and force on
the film web had ~o be limited to a narrow range to avoid
crushing the pallet load or losing containment from some sides of
the pallet load. Therefore, high wrap forces are impossible.
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Also, the corners of the pallet load and the corners of the
individual units making up of the pallet load, when wrapped with
the film web would create a point force loads, on the film web
which cause rupture of the film web at high film web wrap forces.
Finally the Kaufman motor would suffer the same overrun
problems, discussed above, if high wrap forces could otherwise be
attained despite the grossness in load problems. Such overrun
problems would have occurred if the supply speed was substantial-
ly lower than the highest demand rate.
The Anderson Company pallet wrapper, introduced at-the 1978
Chicago PMMI Show and illustrated as prior art in U.S. Patent No.
4,503,658, interconnected the film web supply with the pallet
turntable with a variable transmission. Constant film web supply
speed could be attained and no demand force controlled overrun
problems would occur~ However, the grossness of load and point
source load problems prevented speed and force operation outside
the same range as Raufman. Even if these problems could be over-
come, high wrap forces would prevent an effeetive operation by
dislodging the pallet load from its position.
Film Force Requirements: Use of Conveyors
and Other Bundle Suppor_s
Conveyors and other bundle supports have been used in bundle
wrapping in order to transport and support the bundle during
wrapping. An example of such a system is shown in U.S. Patent
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4,317,322. Howe~er, conveyors and other bundle supports in-
creased the cross-sectional wrappiny area since they were posi
tioned on the outside of the bundle. When using conYeyors and
other supports, the film web would haYe to additionally recover
against the bundle after the bundle had been moved off of the
conveyor because of the cross-sectional area of the bundle rela-
tive to the conveyor and the supports.
The film force limitations of the conventional systems dis-
cussed above are even more critically limiting when used with
lC conveyors and other bundle supports. This is because even
greater force on the film web is required to wrap the bundle on
the conveyor and support so that adequate containment force would
be available subsequent to film web re~overy onto the bundle from
the conveyor and bundle supports after the bundle hAd been re-
moved from the conveyor and supports after wrapping, However, in
order to avoid bundle collapse during wrappin~, the force to the
bundle conventionally was minimized and the recovery of film
agains~ the bundle produced a subst~ntially reduced containment
force.
20 Film Force Limited: Problems
With Multiple Unit ~undles
Multiple unit hundles consist of a number of individual
units, with each unit b~ing a box or carton such as one which is
ultimately delivered to the consumer. The units may be stacked
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both across the width, length, and height of the bundle. Such
bundles of individual units have practically no internal struc-
tural strength since the friction between the units is minimized
by their shape, mass and container surface characteristics.
Therefore, it has been significantly difficult to wrap a bundle
of these individual units with a film web at a wrap force which
is sufficiently hi~h to result in a containment force on the bun-
dles while not skewing the bundles either during or after the
wrapping process. However, multiple unit bundles also have a
10 special requirement for a containment force which is high enough
to form a tight bull's~eye pattern in the film at the ends of the
bundle. A tight bull's-eye means smallness of size of the aper-
ture defined by the film ends on the ends of the bundle after
wrapping, and tightness on the film web on the bundle ends.
Although this is desirable on any wrapped bundle, it is espe-
cially desirable and necessary on bundles having multiple units
to prevent the units from falling out of the bull's-eye or
shifting.
Film Force Limited: Problems W~th Crushinq
2a ~he regulation of wrap force has also been a problem with
fragile crushable bundles. Since only the minimum force is
locked into the wrapped film web due to the varying demand rate
of a non-circular cross-sectioned bundle, such bundles must be
wrapped with a sufficiently high wrap force in order to have a
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sufficiently high containment force. However, the wrap force
also needs to be sufficiently low such that the packages will not
be crushed. The result of this situation is that crushable bun-
dles conventionally are often crushed during wrapping or are
wrapped in film web which provides insufficient containment
force.
Film Force Limited: Problems With Bundles
Having Oblonq Cross-Sections
There is a further aggravating factor ln conventional film
10 wrapping systems which reduces containment forces on bundles
having oblong cross-sections. ~ film web segment applied to any
side of a bundle exhibits elongation and force independent of the
contiguous film web app}ied to either of the surfaces wrapped im-
mediately prior to or after the given side. This is because bun-
dle edges isolate tension on each film web segment applied to a
surface from connecting film web segments applied to adjacent
surfaces. Since slippaqe and tension equalization across edges
does not occur, extreme tension di~ferences exist between the
consecutive segments of a wrapped bundle having an oblong cross-
20 section. Further, since the lo~king in of forces occurred wherethe ~ilm web had recoYered to a minimum elongation, only the min-
imum containment charactistics are locked into the film web.
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sununary
In summary, conventional wrapping systems suf~er from many
drawbacks.
It has been difficult to obtain a high throughput speed,
high film dispenser orbit speed and high film dispensing speeds
due to difficulties in controlling supply of the film web from
the film web dispenser.
It has been difficult to prevent film rupture due to the
grossness of load, point source loading due to corners of a bun-
dle, and uncontrolled high stresses due to uncontrolled~operationof pre-stretch systems due to overrun,
It also has been d;fficult to obtain high containment forces
on the wrapped bundle due to the use of conveyors and other sup-
ports for the bundle due ~o recovery of pre-stretch elongation
which occurred between the film web dispenser and the bundle dur-
ing wrappins.
It has been further difficult to obtain high containment
forces on the wrapped bundle because of the difficultiles in
properly positioning and orienting of the bundle relative to the
20 wrappin~ system.
It has been difficult to prevent the bundle and subunits of
the bundle from being dislodged from the wrapping position due to
the high wrapping force on the film web which is required to pro-
duce an adequat2 containment force on the bundle.
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J~79~15
It has been difficult to prevent crushing of the bundle dur-
ing wrapping due to the wrapping force required in the film web
to produce an adequate containment force on the bundle.
It has been difficult to prevent great changes in stress on
the film dispenser and film web during wrapping due to varying
demand rates caused by film web demand variations in a
non-circular cross-sectioned bundle.
It has been difficult to obtain a,high wrap force due to
bundle sensitivity and difficulties in controlling film supply.
It has been difficult to obtain high elongation of-~he film
web during wrapping for efficient use of the film web while
obtaining high containment forces without rupturing the film;
It has been difficult to equalize locked-in forces in the
film web when wrapping oblong bundles.
It has been difficult to apply wide film web while
minimizing wrinkles in the film web after it.has been applied to
the bundle.
It h~s been difficult to obtain, due to lack of adequate
containment force, a tight bull's-eye pattern in the film at the
ends of the bundle.
In view of these difficulties with conventional systems
there are a variety of objects which the present invention seeks
to achieve.
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It is a further object of the present invention to obtain a
- high throughput speed, high film clispenser orbit speed, and high
film dispensing speeds by effectively controlling supply of the
film web from the film web dispenser while providing high film
web containment force on the bundle after wrapping.
It is an object of the present invention to prevent film
rupture due to the grossness of load, point source loading due to
corners of a bundle, and uncontrolled high stresses due to
uncontrolled operation of pre-stretch systems due to overrun.
It is an object of the present invention to obtain high con-
tainment forces on the bundle while using conveyors and other
supports for the ~undle.
It is another object of the present invention to obtain high
containment forces by properly positioniny and orienting of the
bundle relative to the wrapping system.
It is also an object of the present invention to prevent the
bundle and subunits of the bundle from being dislodged from the
wrapping position due to high wrapping force on the film web
which is required to produce adequate containment force on the
20 bundle.
It is a further object of the present invention to prevent
crushing of the bundle during wrapping due to the wrappin~ force
in ~he film web which is required to produce an adequate contain-
ment force on the bundle.
-2~-
9 ~
It is another object of the present invention to prevent
great changes in stress on the film dispenser and film web during
wrapping due to varying demand rates caused by film web demand
variations in a non-circular cross-sectioned bundle.
It is an additional object of the present invention to
obtain a high wrap force due to bundle sensitivity and difficul-
ties in controlling film supply.
It is also an object of the present invention to obtain high
elongation of the film during wrapping for efficient use of the
film web while obtaining high containment forces without
rupturing the film.
It is also an object of the present invention to equalize
locked in forces in the film web when wrapping oblon~ bundles.
It is an addi~ional object of the present invention to apply
wide film web while minimizing wrinkles in the film web after i~
has been applied to the bundle.
It is another object of the present invention to obtain a
tight bull's-eye pattern in the film at the ends of the bundle.
Additional objects and advantages of the invention will be
set.forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of
the invention. The objects and advantages of the invention may
be realized and obtained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
-~5-
~`
, . . .. : ~ . .
~ ~7g815
S~[MARY OF THE I~JVENTION
To achieve the fore~oing objects, and in accordance with the
purposes of the invention as embodied and broadly described here
in, there is provided a process for wrapping a bundle with a film
web dispensed from a film web dispenser comprising moving a bun-
dle into an applicator mandrel, revolving the film web dispenser
relative to the applicator mandrel, dispensing the film web from
the film web dispenser onto the applicator mandrel at a constant
supply speed, transporting the film web wrapped around the
10 applicator mandrel beyond the downstream end of the applicator
mandrel, continuously moving the bundle beyond the downstream end
into the applicator mandrel, and applying the film web from the
applicator mandrel onto the bundle so as to provide a containment
force in the film web after it is applied onto the bundle.
It is preferable to restrain and retard the film web being
dispensed by the film web dispenser. It is also preferable to
dispense the film web from the film dispenser at a dispenser sup-
ply speed less than the lowest demand speed at the applicator
mandrel.
2a It is pre-stretch the film web beyond its pre-stretch yield
point to plastically deform the film web in a film dispenser and
subsequently post-stretch the film web in the linear
stress-strain range beyond its post-stretch yield point t~ plas-
tically deform the film web between the film web dispenser and
~.
~,t~98~s
the applicator mandrel throughout the ~evolution of the film web
dispenser.
It is preferable to position an oblong cross-sectioned bun-
dle having a wider side and a narrower side in the applicator
mandrel and supporting the film web on the applicator mandrel so
that the cross-section of the supported film web is less oblong
and more square than the bundled cross-section.
It is preferable to prevent the application of substantial
point loads to the film web from the applicator mandrel and sup-
ply a substantially uniform force across the full web width ofthe film web while dispensing the film web onto the applicator
mandrel.
It is preferable to maintain the film web within a
stress-strain variation range wherein film web stress undergoes
minimal variation while film web strain undergoes comparitively
greater variation throughout the revolution of the film web dis-
- penser while the film web is positioned between the film web dis-
penser and the applicator mandrel.
It is preferable to dispense a first film web in a first
helical direction ha~ing a f irst circular component and a second
film web on a second helical direction having a second circular
component opposite to the first circular component.
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1 ~7~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the present prefe,rred
smbodiment of the invention as illustrated in the accompanying
drawings;
The wrapping process of the present invention will be described
as being performed on the dual-dispenser apparatus and also shown in
Figs 1 4 described in ~.S. patent 4,712,354 issued December 15, 1987.
As shown in Fig. 2, a plurality of units 43 forming bundles 40
have been loaded in stacked relationship on an infeed conveyor
assembly 31 either manually or mechanically. As an alternative to
the conveyor, descending freewheel rollers or a pneumatic or
hydraulic pushing device can be used to engage and push each bundle
40 into the wrapping area.
An upstream wrapping stage 35 and a downstream wrapping stage 36
are mounted to frame 38. Each wrapping stage includes a dispenser
barrel 50 for revolving a film roll 56 and a film web dispenser
around a bundle 40. The film web dispenser includes elongation
mechanism 70. The dispenser barrel 50 includes a mounted hoop 52, a
free hoop 54, and a plurality of barrel tubes 53 joining hoops 52 and
54 so that they are coaxial and parallel to one another.
~ s shown in Fig. 3, mounted hoop 52 is bolted or otherwise
fixed coaxially to the outermost race 44 of a circular triple
28
bearing race 42. The middle bearin~ race 46 of a triple race 42
is fixed to the fra~e 38, and the innermost race 48 is freely
driven to rotate for purpo~es which will be described below. A
dispenser motor 60 is mounted to the frame and coupled through
right angle reducer 61 to drive friction wheel 62 which is in
contact with outer race 44. Thus, operation of motor 60 ~ill ro-
tate friction wheel 62, outer race 44 and dispenser barrel 50.
Elongation motor 6~ is couple~ through reducer 65 to reducer
, pulley 63. A belt 59 surrounds pulley 63, tension pulley 66, and
10,' drive pulley 67. Drive pulley 67 is mounted on shaft 6B which in
turn is mounted to the frame 38 and extends inside the inner race
48. As shown in Fig. 4, friction roller 69 contacts inner race
48 and is moun~ed to shaft 68. Therefore, operation of motor 64
will drive the belt 59, the pulley 67, friction roller 69 and
inner race ~8.
The film web dispenser elongation mechanism 70 and film roll
56 are mounted on the dispenser barrel S0 opposite a counter-
weight 90. The elongation mechanism 70 includes an upstream
roller 72 and downstream roller 74 which are driven by elongation
20l¦ motor 64 to rotate at respective fixed constant surface speeds.
Film web 58 is drawn from roll 56 across the surface of the up-
stream roller 72 rotating at a first constant speed and then
across the surface of the downstream roller 74 rotating at a sec-
ond constant speed higher than the first constant speed. The
-29-
~L~'79~
film web 58 is stretched between the upstream and downstream
rollers 72 and 74 at a constant stretch ratio corresponding to
the ratio of the speeds of the upstream and downstream rollers 72
and 74. For film webs which are currently popular, the streth
ratio is preferably in the range of 1:2 to 1,3.
As shown in Fig. 2~ core hubs 91 and 92 are mounted adjacent
to each of the hoops 52 and 54 to engage the hollow core of film
roll 56 and maintain film roll 56 rotatably mounted on the dis-
penser barrel 50. Core hub 92 and disk brake 94 are pivotally
mounted to the hoop 52 by hinge 96. Brake 9~ engages the hub 92
;and restrains the hub 92 from free rotation. This prevents rapid
spillage of film web 58 from film roll 56 during shutdown of the
wrapping operation. Brake 94 also prevents slack on the web be-
tween roller 56 and roller 72 as film payout reduces the diameter
of film roll 56.
As shown in Fig. 4, core hub 9l is mounted to swing plate 93
which pivots across the plane of hoop 54 on pivot shaft 95 jour-
nalled to hoop 54. At an end of sw;ng plate 93 opposite shaft
95, a locking pin 97 is removably engaged with hoop 54. It may
20 be engaged by spring pressure to enter a blind bore of hoop 54,
~or by being threaded to a threaded bore of hoop 54. Handle 98 i5
coupled to pin 97 for manual release of pin 97 from the hoop 54
'when film roll 56 is completely dispensed. Plate 93 and core hub
91 may then be swung away from the roll core about shaft 95, and
~30-
~. ~
iV~ 7sa~
the core may be tilted outward from the hoop 54 on the hinge 96,
shown in Fig. 2. The roll core then may be removed easily by
hand and a fresh film roll 56 may be mounted by engaging one end
of the roll core to hub 92, swinging the roll inward, and closing
swing plate 93 to engage hub 91 with the core of the roll 56.
Pin 97 then is locked into the hoop S~ to maintain new film roll
56 in place.
. As shown in Fig. 13, upstream roller 72 is mounted on up-
, stream shaft 73 one end of upstream shaft 73 is journalled to
10l support plate 79 on hoop 54. The other end of upstream~shaft 73
passes into a transmission housing 71. Downsteam roller 74 i5
mounted on downstream shaft 75. One end of downstream roller 7
is journalled to plate 79 and the other end passes through the
transmission housing 71. An upstream gear 76 is mounted to up-
~stream shaft 73 in housing 71. A downstream gear 78, smallerthan upstream gear 76, is mounted to downstream shaft 75 and is
coplanar with upstream gear 76. The ratio of gears 76 and 7
preferably is in the range of 2:1 to 3:1. Additionally, a ten-
'sion shaft 88 is journalled within transmission housing 71 and a
20lltension gear 87 is mounted to shaft ~8 coplanar with gears 76 and
¦78 so that a chain surrounding gears 76, 78 and 87 will follow a
! triangular path. A transmission chain 77 encompasses gears 76,
,¦78, and 87 to define a fixed speed ratio between gears 76 and 78,
llshafts 73 and 75, and upstream roller 72 and downs~ream roller
" 74.
,
-31-
,
~ 79~3~LS
Downstream drive gear 86 is mounted to downstream shaft 75
in transmission housing 71. A shaft bracket 81 is fixed to hous-
: ing 71 and extends inwardly toward the axis oE inner race ~8. Adrive shaft 83 is journalled to bracket 81 and extends into the
plane of the inner race 48. A drive roller 82 is mounted on
shaft 83 and contacts inner race 48. A drive gear 84 is mounted
. on shaft 83 coplanar with the downstream drive gear 86. A chain
85 connects gears 84 and 86. Therefore, the relative rotation of
inner race 48 and dispenser barrel 50 will drive the drive wheel
10 . 82, the downstream roller 74, and the upstream roller 72 all to
rotate in the same direction. The ratio of gears 84 and 86 is
preferably 1:1 for the sake of convenience although other prede-
termined ratios may be utilized. As barrel 50 rotates, roller
82 will pass by roller 69. The width and position of the rollers
69 and 82 should be chosen so the rollers do not callide during
rotation.
As shown in Fig. 13, free rollers 121, 122 and 123 are jour-
nalled to plate 79 and housing 71 adjacent the roller 72 and 74.
As shown in Fig. ~, the film web 58 is drawn from film roll 56
20llacross first free roller 121, then across ~he surface of down-
stream roller 72, and across second free roller 122 adjacent the
space between roller 72 and 74, across the downstream roller 74,
and across free roller 123. Film web 58 is drawn as far as the
downstream roller 74 by the relative rotation of race 48 and
: -32-
~ 8~ 5
barrel 50, and then across roller 1~3 to the applicator mandrel
180 by relative rotation of barrel 50 and the mandrel 180. All
of the rollers 72, 74, 121, 122 and 123 rotate as the film web
passes across them, and are parallel to the film roll 56 and the
barrel tubes 53. A nonparallel angled free roller 12~ may be
mounted to hoops 52 and 5~ adjacent free roller 123. Film web 58
. passes from free roller 123 across roller 124 and then to the
center of barrel 50 in the vicinity of bundle 40 and applicator
' mandrel 180. The angular placement of roller 12~ advantageously
10.l enhances wrinkle-free application of the film web 58 at the man-
drel. Roller 124 preferably is mounted so that the angle may be
~' adjusted to obtain the optimal film condition. The stretched
film web 58 is drawn during rotation of the dispenser barrel 50
to applicator mandrel 180 through which bundle 40 is transported
during wrapping. As shown in Fig. 22, the mandrel 180 comprises
a film web transporter 108 beneath the bundle conveyor 110, and
at least one film web transporter adjacent at least one addi-
tional side of the bundle such that two film web transporters
carry the film web adjacent opposed surfaces of the bundle.
20!¦ Bundle conveyor 110 preferably includes one or more endless loop
package chains 102 circulating around chain tracks 103. Chain
tracks 103 are spaced sufficiently far apart in main plate 111 of
! conveyer 110 to avoid bundle spilla~e, and are preferably manu-
factured from a class of plastic substances known as ultrahigh
-33-
j
,
'1~ 7 ~ 8~
molecular weight polyethylene. Chain tracks 103 expose the up-
permost surfaces of chains 102 and support the lower surface of
chains 102 against sag when a bundle 40 rests on chains 102. At
a point upstream of dispenser barrel 50, each chain 102 circu-
lates around a gear 112 mounted to an axle 122, then around a
gear 114 mounted to an axle 124, and finally around a gear 116
mounted to an axle 126, before proceeding downstream to carry the
bundle. Main plate 111 of conveyor 110 defines a throughgoing
bore 128 beneath each track 103, through which the returninq
10 chain 102 passes to encounter gear 112.
Film web transporter 108 is positioned beneath the conveyor
110 and preferably includes an endless loop chain 132 circulating
in a downstream direction in chain track 109 beneath the plate
111 and then returning in an upstream directîon through a
throughgoing bore 134 defined by plate 111. At the upstream end,
chain 132 circulates around gear 136 mounted to axle 122. In
this manner, the bundles 40 are carried on conveyor 110 synchro
nized at the same speed as the film web carried beneath conveyor
:L10 by transporter 108. This is accomplished by using identical
2~l gears 112 and 136 on shaft 122 to drive chains 102 and 132.
As shown in Fig. 2, conveyor 110 and transporter 108 may be
driven by mounting gear 196 to axle 194 of motor 195. Gear 197
is mounted on axle 122. Chain 198 circulates about the gears 196
and 197, so that operation of the motor 195 will move the chains
102 and 132 which engage gears 11 and 136, respectively.
' -34-
~7g8~5
At the downstream end of the conveyor 110, each chain 102
passes across the end of track 103 and around a gear 130 mounted
! to freely rotate so that the chain 102 passes from the upper
track 103 flowing in a downstream direction to the throughgoing
bore 128 flowing back upstream, in the reverse direction. Chain
132 circulates about a gear, not shown, mounted to main plate 111
' between the two gears 130. Wheels 200 are mounted downstream
from ~ears 130 on plate 111 and rotate freely with gears 130 suf-
ficiently below the upper surface of main plate 111 to avoid con-
10, tact with the bottom of a bundle. In order to support ~he down-
stream end of conveyor 110 and film web transporter 108, the
bottom edge of each wheel 200 is supported on roller 201 attached
to the frame. Thus, the film web is carried downstream beneath
main plate 111 by the lower exposed portion of chain 132. The
film web does not encounter any opposition to this motion since
the portions of chains 102 and 132 moving upstream are isolated
within bores 1~8 and 134, respectively. When the film web trans-
ported by chain 132 encounters the wheels 200, it passes between
the wheels 200 and the roller 201 and recovers against the bottom
20jlo~ the bundle downstream from the wheels and the roller.
The applicator mandrel 180 includes a bottom film web trans-
porter 108 and at least one other film web transporter which is
adjacent at least one widest surface of the bundle in addition to
transporter 108. If the widest bundle sides are vertical, then
,
i~ ~! ! -35-
, .
;
S
two parallel vertical transporters 210 are preferably utilized as
shown in Figs, 1 through 4. If the widest sides are horizontal,
then one film web transporter 330 is placed atop the bundle and
opposite transporter 108 as shown in Figs. 19 through 21. Each
film web transporter carries the film web 58 wrapped across the
film web transporter in the downstream direction at the same
speed as the bundle speed.
The film web transporters 108 also provide an effective in-
crease in the wrapping radius perpendicular to the widest bundle
10 surface. Thus, the difference between the vertical wrapping ra-
dius and the horizontal wrapping radius of an oblong bundle dur-
ing wrapping is minimized by placement of the film web trans-
porters so that the cross-section of the film web is supported on
the mandrel is less oblong and more square than the bundle cross-
section. The variation in elongation of the film web as the film
web is wrapped across consecutive surfaces of the application
mandrel 180 is more unified and is more easily maintained sub-
stantially in the linear wrap force range according to the pres-
ient invention by this positioning of application mandrel 180.
2~lHigh containment force is obtained at the mandrel and ultimately
lat the bundle.
,I The applicator mandrel 180 preferably extends through bothdispenser barrels 50. However, a first mandrel may extend within
the first dispenser barrel and a second mandrel may extend within
-36-
~'~t79~1 ~
the second dispenser barrel. Alternatively, conveyor 110 and
transporter 10~ may extend through both barrels while film web
transporter 210 or 330 are separately positioned in each barrel.
Certain types of bundles are extremely fragile and may re-
quire film web transporters which extend to cover the entire
adjacent bundle surfaces for preventing the wrapped film web from
imparti~g a substantial part of the wrap force on the bundle.
However, for many other less fragile bundles, significant economy
, can be derived by covering only a portion of a bundle surface
10l with a film web transporter, leaving the bundle edges exposed to
encounter film web 58. Since the topmost lengthwise edges of the
bundle are most prone to disalignment, film web transporters 210
or 330 preferably extend across bundle surfaces to a distance
from bundle ed~es no greater than 1/2 of the height or width, re-
spectively, of bundle units at each edge.
The effect of this placement on film demand is shown in Fig.
16 in which a rectangular bundle with 10 inch vertical surfaces
and 14 inch horizontal surfaces is placed between a top surface
Ifilm web transporter 330 and the conveyor 110 and bottom surface
20lfilm web transporter 108. For purposes of illustration, it is
assumed that the film web transporters are 2 inches thick. At
the downstream end of the transporters, the film web recovers to
the top and bottom surfaces of the bundle, and the final circum-
ference around the bundle is 48 inches.
!
~ ~ I
I -37-
~ ~,'79~5
With very fragile bundles, the film web transporters prefer-
ably extend across the full l~ inch width of the top and bottom
bundle surfaces in the applicator mandrel. In th;s case, the
mandr-el wrapping circumference is 56 inches and the film web re-
covers by 16% to reach the final circumference of 48 inches at
the downstream end of the applicator mandrel when it moves from
the mandrel to the bundle. Furthermore, the maximum wrapping ra-
dius B is 9.9 inches and the minimum radius A is 7 inches, with a
ratio of minimum to maximum of 0.71 and a difference of 2 9
inches. Thus, the placement of the film web transporters present
a wrapping cross-section which reduces the range of elongation
! variance during wrapping of the applicator mandrel.
As shown in Fig. 17, as preferred for somewhat less fragile
bundles, the width of the film web transporters and conveyor is
reduced to 10 inches to obtain an octagonal cross-section in the
applicator mandrel for wrapping with both the bundle edges and
the film web transporter ed~es encountering wrapped film web 58.
The wrapping circumference of the applicator mandrel is then 51.3
inches, and the film web must recover only 6.9% to reach the
201l final bundle circumference of 48 inches. The maximum wrapping
I radius is reduced to 8.6 inches, so tha~ the minimum to maximum
ratio is increased to 0~81 and the difference or range of radii
is reduced to 1.6 inches. Thus i~ is apparent that a very modest
reduction in the transporter width achieves s;gnificant
-38-
~,>7~
improvement in final bundle force after recovery by the film web
beyond the downstream end of the applicator mandrel, while simul-
I taneously requiring a linear wrap force range of lesser width and
permitting higher pre-stretch ratios. It is useful to reduce the
width of each transporter so tha~ its outermost edges are at a
radius, or distance, from the center of dispenser rotation no
I greater than the distance from the dispenser rotation center to
! the bundle edges as shown in Fig. 17.
l While those skilled in the art will recognize that~the pre-
Icise calculations will vary depending on the thickness of the
film web transporter and the cross-section dimensions of the bun- ;
,dle, it can be seen that significant advantages are achieved in
Iboth final force and final film elongation by the present inven-
ltion, which in turn reduces the operating consumption and total
lcost of the film web.
As shown in Fig. 9, by comparison, the 10 inch by 14 inch
bundle conventionally would be supported only by a 10-inch-wide
.conveyor 110 and bottom film web transporter 108. Presuming that
,the bottom supports 108 and 110 total 2 inches in height, that
2~¦the bundle is centered and that the film web recovers between the
dispenser and the bundle, then the maximum wrapping radius B is
9.2 inches while the minimum radius A is 6 inches, for a ratio of
.65 and a difference of 3.2 inches. The recovery at each side is
thus at least 35% during wrapping and an additional 3.2% (49.6
l -3~-
,
'
79~3~5
inches to 48 inches) when the bundle exits the conveyor,
with additional recovery between the pre-stretch subsystem
and the bundle of 33~ to 50~.
Generally, the width of the conveyor 110 may be reduced
where the bundle rests in a tray during wrapping. This is
oten the situation when wrapping for example, cases of
sot-drink cans or bottles, or where a single, relatively
stiff unit comprises the bottom of any wrapping cross-
section. In the illustrated mechanism, the mere use of
chain as a minimum-width film transporter 108 presents a
modest further reduction in final recovery at the end of
application mandrel 180 but does not further decrease the
range of wrapping elongation variance since the demand
speed maxima and minima remain constantO The width of top
film web transporter 330 may be reduced so that the edges
of transporter 330 preferably span at least half of the
width of outermost top bundle units in the horizontal
direction transverse to the motion of the bundle.
Likewise, the height of transporters 210 preferably spans
at least half the height of outermost top bundle units.
Alternative film web transporters beneath the bundle
are descxibed in U.S. Patent No. 4,317,32~ assigned to
Lantech, Inc.
Figs. 2. through 4 show a film web transporter
arrangement which is preferable when the wider side of
an oblong bundle is
-40-
S
vertical. Film web transporters 210 are positioned in close
. proximity or in contact with opposing widest surfaces, which are
! vertical, of the tall bundle 40. Each film web transporter 210
comprises a skid-sleeve 178 secured to the frame, and upstream
double-sheave pulley 172 and downstream pulley 174 mounted at op-
posite ends of the skid-sleeve 178. A belt or chain 170 encir-
cles one sheave of pulleys 172 and 174. Belt 170 circulates in a
downstream direction toward pulley 174 while exposed at an upper
, edqe of skid-sleeve 178 toward pulley 172. Upstream pulley 172
lO is preferably located upstream from the wrapping station 41,
while the skid-sleeve 178 preferably extends downstream thro~gh
and beyond the wrapping station. Generally, each skid-sleeve 178
'extends vertically across an entire vertical face of bundle 40,
.but for sturdy bundles may be abbreviated to extend across merely
a portion of the bundle face.
Transporter motor 162 is mounted to a lower portion of frame
38, and rotates motor shaft 164 about its axis. Shaft 164 ex-
tends outwardly on opposite sides of motor 162, Pulleys 168 are
imounted to opposite ends of axle 164 below respective pulleys
2ql172. Each pulley 168 and a second sheave of the respective pul-
ley 172 are encircled by a vertical belt 169. Therefore, opera-
tion of motor 162 will drive the circulation of side conveyor
belts 170. As the upper portion of each belt 170 moves down-
'stream, it carries with it any film web 58 which may be wrapped
.j
-41-
.
9 ~
around the skid-sleeve 178. The skid-sleeve 178 is preferably
configured and composed of a material chosen for low friction
with the film web 58.
~ igs. 19 through 21 show a film web transporter arrangement
which is preferable when the wider side of an oblong bundle is
horizontal. A top conveyor 330 is driven to carry film web 58 is
wrapped along the top of the conveyor 330 in said downstream di-
rection at the same speed as the bundle~ The top conveyor 330
~comprises belts or chains 332 rotating across upstream rollers
10, 334 and downstream rollers 336, beneath conveyor support plate
338. The rollers 33~ and 336 are journalled to the support plate
338. Support plate 338 extends upstream from the wrapping area
and is fixed to the frame of the apparatus to support top con-
veyor 330. Motor 340 and dual output reducer 34~ are mounted to
frame 38 upstream of the wrapping area. Motor shaft 3~2 is cou-
pled to reducer 34~, and the output shafts of reducer 34~ are
coupled to rollers 33~. Motor 340 will drive rollers 334 to ro-
tate in opposite directions and move the outer portions of belts
332 downstream with the bundle.
20l Other greatly preferred film web transporter arrangements
are shown in Fig. 16 and 17. ~elts or chains 332a and 132a form
the ed~e surfaces of the film transporters 108 and 330 to suspend
the film web between them. This arrangement has proven espe-
cially usefuI in defining the mandrel for wrapping fragile
~i ~ bundles.
,
,
-42-
7 ~
This construction allows the film web to be wr-apped around a
bundle ~0 c:arried from the infeed conveyor 31 onto the wrapping
station 41. The stretched web is initially wrapped around the
bottom tansporter lOa and either two side conveyors 210 or a top
conveyor 330, with ~oth the bundle and wrapped film web being
carried by the conveyor assembly and transporters in the same di-
rection. The film web applied to mandrel 180 forms a tube which
moves off the the downstream end of mandrel 180 and recovers,
still under tension onto the bundle ~0 emerging from within the
10 mandrel. Even if the application mandel is wrapped with a very
high wrap force, the uniform partial recovery of film web allows
fragile bundles to experience balanced forces on opposing sur-
faces which are reduced from those on the application mandrel.
This avoids bundle collapse which would have occurred using con-
ventional arrangements at high wrap forces.
, As shown in Fig. 18, the bundles 40 preferably are spaced
;apart so that the continuous film web tube between consecutive
bundles can be severed by any conventional cutting device 400
jidownstream of the mandrel 180. Continuously wrapped bundles are
201taken off of the apparatus and are severed into separate bundles
on conveyor 33 away from the apparatu~. According to the present
invention, the film web tube portions extending before and behind
bundles after severance promptly recover under tension against
respective leading and trailing ends of the attached bundle to
: '
i:
-43-
.
3~3~S
form tight bull's-eye patterns 40a on the ends of the
bundle. The containment force exerted Oll bundle ends is
improved due to the higher force applied when the ~ilm web
encompasses the bundles and the spaces therebetween.
Infeed conveyor 31 brings each bundle 40 onto conveyor
110 which then carries the bundle through each of the two
wrap stations 41 within the applicator mandrel 180. At
startup, the leading edges of the film webs 58 are held
beneath transporter 108. One way to hold the webs at
startup is to tie the leading end of the web 58 from stage
35 to the leading end of the web 58 from stage 36 beneath
transporter 108. As shown in the above-mentioned U.S.
patent 4,712,354, each dispenser 41 is positioned and
arranged to orbit the applicator mandrel in a direction
opposite that of the other dispenser 41, so that the two
wrap patterns placed on each bundle will have opposite
circular components due to the orbiting dispensers
and identical linear components due to the motion of the
mandrel and bundle.
As each barrel 50 rotates, film is drawn across the
surface of downstream roller 74 to encircle the applicator
mandrel 180. The rotation speed of roller 74 is
proportional to the rotation speed of the race 44 and
independent of the demand for film web 58 at the bundle.
If chain 77 engages gears 76, 78 and 87, then the rota~ion
speed of upstream roller 72 is held to a constant ratio of
that of downstream roller 74, so that upstream roller 72
-44-
B
~,79~3~5
draws film 5~ from film roll 56. The film web is stretched both
duriny passage between the rollers 72 and 74, due to their rela-
tive speed ratio, and between roller 74 and the applicator man-
drel. Alternatively, roller 72 can be removed or allowed to
freewheel by removing chain 77 or by disengaging gear 76 through
a clutch mechanism so that no pre-stretch is exerted on web 58
but the web 58 is still drawn to and dispensed across roller 74
at a substantially constant supply speed and is stretched between
Iroller 74 and the mandrel.
At the improved operating speed of barrel 50, which is typi-
cally ~0 to 60 rpm, the high demand speed of film web 58 at man-
drel 180 causes elonqation of web 5~ at the mandrel substantially
beyond the yield point of the film web between the film web dis-
penser and the applicator mandrel. The stress-strain character-
istics of the film web in this area are within the corresponding
linear wrap force range. The direction of the wrap force varies
as the film web dispenser orbits the applicator mandrel 180.
However, applicator mandrel 180, which includes conveyor 110 and
transporter 108 in combination with transporter 330 or trans-
20lporters 210, supports the bundle and resists the force from any
iof its directions.
j Thus, the present invention achieves significantly increased
~¦operating speeds without compromising reliability or increasing
the rate of failure of the film web. The film web rem~ins intact
! 45
:~ ;
~ ~ 7 ~ ~ S
even if a hole develops in the ilm web. This is because the
controlled supply system wilL continue to dispense film indepen-
l dent of its being weakened by the hole. Thus, no dispenser or
! pre-stretch mechanism shut-down occurs.
After one wrap has been made around the mandrel 180, the
leading edge of the web 58 is held firmly beneath the overlying
web 58. A number of wraps are placed around the mandrel which
'carries the wrapped web and the bundle downstream. The combina-
,ltion of dispenser circular motion and mandrel/bundle linear mo-
l0lltion creates a helical wrapping pattern with a first circular
component at the first dispenser and a second circular component,
opposite to the first, at the second dispenser. It should be
noted that there is a space between the downstream end of
lapplicator mandrel 180 at the second wrapping stage and the
itake-off conveyor 33 allowing the stretched film web to recover
from the larger mandrel circumference to the smaller circumfer-
ence of the bundle emerging from the mandrel, applying opposing
forces simultaneously to opposite bundle sides. The reduction in
web circumference is accompanied by a reduction in bundle force,
201¦thus avoiding the bundle crushin~ and the film web failure expe-
¦rienced at peak forces in the prior art.
n the continuous wrapping operation, the bundles are con-
¦tinuously carried along the wrapper conveyor assembly to the end
lof the applicator mandrel, and then onto take-off conveyor 33.
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The bundles are then severed between the spaced film areas as
previously discussed and taken away to another transport area
The present invention is directed toward a process which
avoids the dilemma of simultaneous high-force hazards o~ film web
rupture and low-force inefficiencies due to unreliable contain-
'ment present in conventional wrapping systems. It does so by
;Imanaging the supply speed and stress-strain characteristics of
the film web and preventing the force on the film web from con-
ltrolling the supply speed of the film web from the film web dis-
lO Ipenser. The process markedly increases the final eontainment
force of the film web on the bundle, reliably avoids both bundle
failure and film web failure during wrappin~, minimizes wrinkles
in wide film web, and permits operation at higher throughput and
film web speeds than previously possible in conventional systems.
In accordance with the present invention, there is provided
a process for wrapping a bundle 40 with the film web 58 dispensed
from a film web dispenser 70 comprising moving the bundle 40 into
an applicator mandrel 180r revolviny the film web dispenser 70
l~relative to the applicator mandrel 180, dispensing the film web
20 l180 from the film web dispenser 70 onto the applicator mandrel
¦180 at a constant supply speedl transporting the film web 58
wrapped around the applicator mandrel 180 beyond the downstream
end of the applicator mandrel 180, continuing moving the bundle
40 beyond the downstream end of the applicator mandrel, and
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applying the film web 58 from the applicator mandrel 180 onto the
, bundle 40 so as to provide a containment force in the film web 58
after it has been applied onto the bundle ~0.
The supply speed of the film web at the film web dispenser
is preferably pre~ented from increasing by restraining and re-
tarding the film web being dispensed by the film web dispenser at
a dispenser supply speed less than the lowest demand speed at the
applicator mandrel.
According to the present invention, the film web is
lO,stretched between the film web dispenser and the applicator man-
drel. Such stretch can be identified by observing a film web
marked at regular intervals which are spaced farther apart on the
wrapped objects such as the applicator mandrel than between the
pre-stretch rollers in the film web dispenser.
Fig. 5, shows that the speed of film take up or demand at
the wrapped object indicated by the curve 150, varies as the bar-
rel 50 rotates about the rectangular mandrel 180 and bundle ~0.
In particular, a minimum point 152 occurs as each edge IS encoun-
tered and is folluwed by a maximum point 154.
20ll Fig. 6 illustrates a film payout speed or supply function,
indicated at 162, which is exhibited by the present invention at
~the downstream roller 74 of the film web dispenser. This shows
~'that the supply function is substantially constant or flat even
~at the high speeds of operation. Regardl~ss of the demand for
a-
il
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film at the bundle, the supply speed of film at the downstream
roller 74 is controlled so as to remain constant while barrel 50
and race 48 each operate at constant speed.
Fig. 7 illustrates a curve of the force and elongation of
the film web an the bundle in which film web force and elongation
is locked in at each bundle edge at each minimwn point 142 below
' the prior maximum point 144 where elongation was greatest. In
conventional bundlers, elongation at the wrapped object fluctu-
ated in a similar pattern. However elongation was always less
10 ; than pre-stretch elongation. Also, the the maximum force corre-
; sponding to point 144 was always reduced by the mechanical advan-
tage or motor torque of the pre-stretch devise to a force sub-
stantially less than the force exerted on the ~ilm web between
the pre-stretch rollers.
In accordance with the present invention, the film web is
stretched beyond its yield point to plastically deform the film
.eb between the film web dispenser and the applicator mandrel
throughout the revolution of the film dispenser about the
applicator mandrel. It is further in accordance with the present
20jlinvention to maintain the f ilm web between the film web dispenser
and the applicator mandrel in the linear stress-strain range be-
yond the yield point throughout the revolution of the film dis-
penser wherein the film web stress undergoes minimal variation
while film web strain undergoes comparatively greater variation
q, g _
throughout the revolution of the f:iLm dispenser while the film
web is positioned between the film web dispenser and the
applicator mandrel.
In accordance with the present invention, if the bundle is
substantially ob~ong in cross-section, the film web is prevented
from substantial pre-stretching prior to dispensing the film web
from the film web dispenser. However, with bundles less oblong
in cross-section, the film web is pre-stretched beyond its pre-
stretch yield point to plastically deEorm the film web in the
film web dispenser prior to subsequently post-stretching the film
web beyond its post-stretch yield point to further plastically
deform the film web between the film web dispenser and the
applicator mandrel.
When initial s~retch beyond the pre-stretch yield point
range of 141 of film web 58 is isolated between upstream roller
72 and downstream roller 74, secondary stretch between the down-
stream roller and the applicator mandrel causes the film web 58
to follow a ~orce-elongation curve 275, illustrated in Fig. 14.
. This curve exhibits a secondary linear wrap force range 277 be-
20 I tween the secondary yield point range 241 and the break point249. The secondary yield point 241 is found at elongations and
. forces slightly lower than at pre-stretch operating point 14a,
; and increases when pre-stretch elongation is increased. The
range 277 generally is found at higher elongations and lower
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forces than the pre-stretch operating point 14a. The present
! invention preferably utilizes a portion of the linear wrap force
range 277 exemplified by the minimum 276 and maximum 278. Force
and elongation are locked in at minima 276 and, as the bundle and
film web moves beyond the applicator mandrel, recovery produces a
bundle force and elon~ation at recovery point 279, well above the
final force and elongation at point 142 which was that at which
~ conventional processes operated.
I To perform the process of the present invention without pre-
lO, stretching the film web, upstream roller 72 is allowed to
I. freewheel by removing chain 77 or otherwise decoupling gears 76
and 78 in any well-known conventional manner Alternatively;
roller 72 could be removed. This results in a different
I stress-strain relation on the film web between the downstream
roller 7~ an application mandrel 180. In accordance with the
present invention, if the film web is stretched only between
downstream roller 7~ and applicator mandrel 180 its stress-strain~
relationship is shown in Fig. 15 as curve 273. This curve exhib-
I its a broad yield point region 272 followed by a broad linear
20 ¦ wrap force range 271 during which plastic deformation occurs in
¦ the f ilm web. This linear wray force range is broader than the
il linear wrap force range 277 for pre-stretched film.
¦ In this non-pre-stretched situation, where initial stretch
' occurs over a long film path, the web width is reduced
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considerably during stretch between the dispenser and appLicator
mandrel laO. This phenomenon is known as neckdown. Neckdown can
; be sharply inhibited by pre-stretching the film web between
closely spaced rollers prior to wrapping the film web on
applicator mandrel 18Q. The force level or stress in range 271
is generally lower than at pre-stretch film webs in pre-stretch
operating point 1~8 or range 277. The linear wrap force range
; 271 extends between the broad yield point range 272 and the break
point 250 over a wider variation of strain elongation. Yield
10 point range 272 occurs at a slightly lower strain elongation and
force level or stress than the pre-stretch yield point 141 be-
tween rollers. According to the present invention, it is prefer-
able that in the non-pre-stretch embodiment, elongation is varied
between exemplary maximum 270 and minimum 274 as each side of the
applicator mandrel is wrapped. Force and elongation are locked
in at each minimum 274. As the bundle and the the web move be-
yond the applicator mandrel 180, recovery of the film web onto
the bundle produces film web stress-strain conditions at point
2807 While strain elongation at point 280 without pre-stretch
201may or may not be as great as that of conventional processes, de-
ipending on the contour of the applicator mandrel, containmentforce of the film web on the bundle ~0 is significantly improved.
According to the present invention, the film web is dis-
pensed from downstream roller 7~ at a constant supply speed.
,
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Downstream roller 74 of the film web dispenser and thus the film
web is restrained sufficiently below the lowest takeup or demand
speed at applicator mandrel 180 to apply stretch to the film web
' between the dispenser and the mandrel substantially within the
gentle sloped linear wrap force ranges 271 or 277 of the respec-
tive curves 273 and 275, depending on whether or not the film is
. pre-stretched. Due to the gentle slope of the curve in this
range, the mandrel 180 as well as the film web and thus the film
web dispenser experiences a substantially constant wrap force re-
10 gardless of variation in elongation due to the varying demand forfilm web as it crosses the mandrel edges during wrapping. The
lapplicator mandrel then releases the film web to encompass each
: bundle at a non-crushing bundle containment force lower than the
wrap force on the mandrel due to the decrease in cross-section
from mandrel to bundle.
As the init;al pre-stretch ratio exerted between upstream
roller 72 and downstream roller 74 is increased, the stress force
level of the secondary linear wrap force range 277 will increase,
neckdown of the web between the downstream roller and the mandrel
201will decrease, and the span of secondary elongation within the
range 277 will decrease~ Conversely, reduction of the pre-
str~tch ratio will decrease the secondary constant wrap stress
force level, increase neckdown, and increase the "width, n or
range of stretch, of the linear wrap force range 277. Therefore,
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the process is preferably used at lesser pre-stretch when
wrapping wider or taller mandrels and delicate bundles that re-
quire low force. The rotation rate of inner race 48 is adjusted
in order to raise or lower the supply speed of the film web, in
order to accomodate a change in demand rate for bundles of a dif-
ferent shape or size. It may also be necessary to configure the
applicator mandrel to extend entirely across bundle surfaces of
delicate bundles, so that the mandrel incurs a large portion of
the wrap force.
lol While the use of pre-stretched film web is more economical,
film web with little or no pre-stretch may be useful where the
oblong bundle configuration causes extreme web takeup speed vari-
! ationsO In such situations, the wide linear wrap force range 271
of stretch of non~pre-stretched f ilm web accommodates the takeup
speed variations.
Certain types of bundles show extreme differences in height
relative to width. These include both extremely tall bundles and
extremely wide bundles. Such bundles exhibit the most extreme
variations in web takeup speed and require the widest linear wrap
291force ranges 277 or 271. An ideal bundle without s~retch varia-
tion would offer a circular wrapping cross-section centered on
the axis of revolution of the dispensers. Among rectangular bun-
dles, a square cross-section centered on the axis of revolution
of the dispensers exhibit minimal variations in takeup speed and
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secondary stretch. According to the present invention, the
wrappiny cross-section experienced by the film web is modi~ied in
order to minimize differences between height and width, and
thereby minimi~e fluctuations in elongation above the yield
point. At the same time, this system advantageously prevents
disruption of the multi-unit bundle by the high, though constant,
wrap force.
Cross-section adjustment is accomplished by placement of
I applicator mandrel 180 in the wrapping area surrounded by barrel
10 ' 50, preferably centered on the revolution axis of race ~.
One way to confirm that the system is stretching the film
i web in its linear wrap force range between the dispenser and the
applicator mandrel is to establish the stress-strain curve of the
film web by dispensing the film web through a load cell between
the dispenser and the applicator mandrel while observing the
elongation of the film web. After knowing the range of the lin-
ear wrap force region of the curve, the controls of the
dispensing mechanism can be set to provide the stress and strain
, on the film web necessary to place it in the linear wrap force
20,~ region.
In accordance with the present invention, this system of
stretching provides higher final stretch, higher bundle contain-
ment force on the film web, higher throughput, and use of less
uniform film while preventing film web breakage than were
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.,
previously through possible. Such web stretch at the wrapped ob-
ject, as opposed to web recovery minimizes wrinkles in a wide
web, conserves film by establishing containment with fewer web
layers, and provides a tight bull's-eye in the film web at the
ends of the bundle.
In accordance with the present invention, the film web is
pre-stretched in the film web dispenser at a sufficient pre-
stretch force and mechanical advantage so that it is beyond its
pre-stretch yield point and subsequently further elongated by
10 post-stretching the film web between the film web dispenser and
the applicator mandrel beyond its pre stretch yield point at a
post-stretch force which is less than the pre-stretch force and
greater than the pre-stretch force reduced by the mechanical
advantage of the pre-stretch system. It is preferable to main-
tain the film web beyond its post-stretch yield point throughout
the revolution of a film dispenser while the film web is posi-
tioned between the film web dispenser and the applicator mandrel.
Under these conditions, the present invention avoids the overrun
condition which occurs in conventional pre-stretch dispensing
20'systems when the wrap force exceeds the pre-stretch force reduced
by the mechanical advantage.
, As shown in Fig. 2~, the supply speed control mechanism of
,the present invention prevents the supply speed of the film web
from increasing and also prevents the supply speed of the film
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web from decreasing. This is accomplished by using a motor driv-
ing the rollers of pre-stretch device which is controlled by a
speed control device with regenera~ive capabilities which can
prevent the speed of the motor from increasing as well as
decreasing. Although motor controllers with regenerative capa-
bilities are known in the motor control art, conventional
wrapping devices did not have a control which prevented the sup-
ply speed from increasing, but rather only had a control that
i prevented the supply speed from decreasing. A motor control wi~h
10, regenerative capabilities would be known in the motor control art
as a two quadrant controller since it could drive or retard a
motor in a controlled fashion which is turning in a positive for-
ward direction. Motor control used on conventional wrapping de-
vices would be known in the motor control art as a single quad-
rant controller since it could only drive, and not retard, a
motor in a controlled fashion which is turning in a positive for-
ward direction.
The positioning of the applicator mandrel according to the
teachings of the present invention accomplishes many of the ob-
20j jects of the present invention. Since the film is wrapped aroundthe applicator mandrel, higher film force may be used to prevent
crushing/ twisting, dislodging or shifting which would occur in
! conventional arrangements. According to the present invention,
when the film web tube formed on the applicator mandrel is
-57-
.
released to surround each bundle it is done so by contacting the
bundle on opposing surfaces simultaneously rather than exerting
force on single bundle edges and sides so that wrap forces are
mutually opposing and balanced. Also according to the invention,
by suspending the film web on an applicator mandrel, forces are
locked in on the film web on different sides of the applicator
` mandrel. Transferring the film web in its suspended state rom
the applicator mandrel to the bundle, the film web reduces the
difference between the locked in forces on its sides, therefore
retaining more even locked in containment forces on the-various
sides of the bundle. This is especially true when either or both
the bundle and the applicator mandrel have oblong cross-sections.
Considerations of dislodging, crushing, and good containment
characteristics of a film web at the end of the wrap bundle, such
that a tight bull's-eye is provided, it is especially important
when wrapping a bundle having a plurality of bundle units.
According to the invention, it is preferable in such circumstanc-
es to position the plurality of bundle units to form a bundle
having as square a cross-section as possible.
In accordance with the present invention, problems with
grossness of load and point source loading which have a tendency
to rupture the film web in conventional systems, are prevented
~hrough the uniformity and controllability of the shape of the
applicator mandrel. Further, the surface of the applicator
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mandrel is such that a substantially uniform force is applied
across the full width of the film web while dispensing the film
web onto the applicator mandrel. Although the applicator mandrel
may contain linear edge lines in some embodiments, there are no
corners, which would otherwise be present from the bundle which
give rise to destructive point source loading at high wrap forc-
es.
In addition, in accordance with the present invention, the
grossness of load problems are solved by wrapping bundles of a
sufficiently small size such as those that can be grasped and
carried by a person and constitute a unit of a pallet load, and
such as bundles in which the greatest cross-sectional measurement
is not substantially greater than two feet square. Also in
accordance with the present invention, bundles of uniform cross-
section are used when continuously wrapping bundles with a system
such as the dual stage orbiting dispensers.
According to the present invention, high throughput is pos-
sible since the film web dispenser can be revolved around the
applicator mandrel and the bundle above the 25 revolutions per
minute previously thought to be a maximum while using convention-
al systems. According to the present invention, the film web
dispenser is revolved around the applicator mandrel on the bundle
at a rate of at least about 30 revolutions per minute and is
,preferably operated in a range of about 40 to 60 revolutions per
minute.
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Additional advantages and modifications will readily occur
to those skilled in the art. The invention in its broader
aspects is, therefore, not limited to the specific details, rep-
resentative apparatus and illustrative examples shown and de-
scribed. Accordingl~, departures may be made from such details
without departing from the spirit or scope of applicants general
inventive concept.
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