Note: Descriptions are shown in the official language in which they were submitted.
1 31 1 1 ~6
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STRETCH WR~PPING ROBOTIC PALLETIZER
This invention discloses and concerns a robotic
article stack unitizer having the capability of receiving
discrete articles from a source of supply, transferring
those articles to an article stacking station where the
articles are stacked on a "pull sheet," a base sheet, in
a low sided box, on a pallet or directly on the surface
of the article stacking station and then providing a film
wrap around the stacked articles in order to "build" a
stable unitized or palletized load~ For readability of
this specification the terms "palletizer" and its
derivatives such as "palletizing, palle-ti~ed, pallet" and
the like is used to mean any type of stacked article
unitizing where the articles are stacked on a pallet, a
sheet surface or on the surface of the unitizers
turntable where no bottom sheet or pallet is used.
In prior art palletizing systems it has been normal
prac~ice to feed or Serve a product to a pallet supported
on a work stand. Each article, or groups of articles
making up a palletized load, would be placed on the
pallet in a location to maximize the number of elements
that can be stacked on a pallet while also attempting to
interlock ~he elements in order to provide some st~bility
to the load once it has been fully accumulated on the
pallet.
After stacking articles or elements to form a full
pallet the full pallet is then removed from the work
stand and delivered to a wrapping station having a
strapping machine, a shrink wrapping machine, a stretch
wrapper or other type of wrapping equipment. At this
wrapping station the palletized load is wrapped or banded
in order to provide con-tinuity and stability to the load.
The apparatus or device presented in this disclosure
is an advanced robotic palletizer or stack unitizer,
which in itself is an advanced palletizing unit that
13~ 1 i86
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incorporates a programmable material handling element
that will typically pick up an article or articles to be
stacked from a supply conveyor or location and then
position these articles on a pallet or on previously
palletized articles. The programmed material handling
element will stack the articles in a preassigned location
on the pallet that will provide a degree of load
stabilization by the interlocking, or overlapping or
cross stacking of the articles on the pallet. Such
interlocking is not a true interlocking of stacked
articles but is more of an overlapping of boxes stacked
on one another 50 tha-t straight columns are not formed of
the boxes or articles being stacked. In many cases the
palletized loads are not significan~ly stable.
Integral with the advanced robotic palletizer is
equipment that allows the robotic palletizer to wrap the
stacked pallet in a film of plastic material that assists
in stabilizing the palletized load,
The robotic palletizer is provided with sensors or
alternatively a preprogrammed sequence of operations,
that direct the palletizer to initiate wrapping of the
load at the most favorable intermediate layers, prior to
the final stack height and complete wrapping of the load.
A film supply source is supported on the palletizer
equipment and can move vertically as film is being
unwound, being guided by various guide rollers, to wrap
the accumulated articles on the pallet as the pallet is
being "built".
One of the advantages of the invention is that
column stacks of boxes or articles can be made since the
pallet load is wrapped at intervals during the building
of the palletized load thus increasing the stack
integrity. By allowing column stacks, rather than the
interlocked stacks of previously known palletizers, the
inherent strength of the boxes or cartons can be utilized
in order to create strong unified, unitized stacks of
131 1 1~6
products. This of course allows greater stack height,
heavier loads, more dense loading on a pallet resulting
in better pallet utilization and the advanta~es attendant
thereto such as decreased shipping costs, and of utmost
importance a decrease in damage to the carton contents
resulting from collapse of the boxes on the lower levels
of the stack.
According to an aspect of the invention, an
apparatus for creatin~J a unitized stack of articles by
alternatively forming a layer of articles and wrapping
the layer of articles without the need for ~n article
guide frame, the apparatus comprises:
a turntable mounted at a fixed vertical height for
supporting the stack of articles;
a palletizer for stacking a layer of the articles on
the turntable or on a previously deposited layer of
articles by selectively placing less than a complete
layer of articles on the turntable and subsequently
placing additional articles on the turntable until a
complete layer of articles has been formed;
wrap means serving means for serving wrap means to
the turntable to wrap a layer of articles unsupported by
a guide frame while the turntable is rotated after the
palletizer has located the articles to form a complete
layer of articles on the turntable or on a previously
formed layer and prior to the palletizer locating
subsequent articles on the previously deposite~ articles;
cutting element means for severing the wrap means
a~ter the wrap means serving means has served wrap means
to multiple layers of articles stacke~ on the turntable
hy khe palletizer.
According to another aspect of the invention,
an apparatus for the construction of a unitized load of
individual articles laterally unsupported by the
apparatus, the articles unitized through the use of film
wrap on the articles after a plurality of articles making
up a layer of articles is placed on the apparatus before
1~
131 1 1~6
subsequent articles for making up a subsequent layer of
articles are placed on the apparatus, the apparatus
comprices:
a turntable means capable of rotation and having a
deck surface equipped with transport means for supporting
the unitized load of individual articles;
input station means for accumulating individual
articles proximate to the turntable means;
mast means supported vertically adjacent the turnta-
ble means;
boom means carried on the mast means, the boom means
movable vertically along the mast means;
gripping means carried on the boom means for grip-
ping articles, the gripping means positionable over the
input station means and the turntable means;
wrap means unwind stand carried on the mast means,
the wrap means unwind stand movable vertically along the
mast means;
wrap means clamp for restraining the wrap means
mounted on the turntable means;
wrap means guide arm between the wrap means unwind
stand and the wrap means clamp for guiding the wrap means
from the unwind stand to the turntable means to wrap a
layer of unsupported articles prior to the grasping means
locating a subsequent layer of articles on the stack.
According to a further aspect of the invention, a
method of unitizing a stack of articles including the
steps of:
feediny an empty pallet means to a turntable, the
turntable stabilized at a fixed location;
picking up a number of articles to be stacked from a
stationary conveyor;
transferriny the articles to the pallet means;
repeating the pick up and transferring steps for a
predetermined number of pick ups and transfers to form a
layer of articles;
~ 3 1 1 1 86
3b
rotating the turntable ater a layer of articles has
been formed;
feeding film from a film storage roll to the
rotating turntable as the turntable rotates to wrap the
layer of articles before further articles are transferre~
to the pallet means;
repeating the step of repeatiny the pick up and
transferring steps for a predetermined number of pick ups
and -transfers to form a layer of articles, the step of
rotating the turntable after a layer of articles has been
formed, ancl the step of feeding film from a film storage
roll to the rotatiny turntable as the turntable rotates
to wrap the layer of articles until a unitized stack of
articles is formed on the turntable;
cutting the film after at least one rotation of the
turntable.
Many other advantages of this invention will be
apparent from a careful perusal of this specification and
disclosure when read in conjunction with the drawing
figures provided herein.
Brief Description of the Drawing Figures
Figure 1 is a simplified isometric presentation of
the invention;
Figure 2 is a plan view of Figure l;
Figures 2A through 2F are plan views of alternative
infeed ancl outpu-t conveyor arrangements;
Figure 3 is a schematic of the film pass line
through the apparatus;
Fiyure ~ is a pictorial plan view of Figure 1;
Figure 5 is a pictorial plan view of Figure 1;
Fiyure 6 is a chart showing timing elements on a
revolution o:E the turntable;
Figure 7 is an alternative embodlment of a portion
of the,invention.
Detailed Description of the Invention
The Figure 1 presentation shows the general
arrangement of the palletizer and this figure will be
i ~
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3c 131 1 1~6
clescribed first. Like reference charac-ters in the other
views represent the same parts as in this view.
The palletizer, generally lO, is made up of three
major components. The turntable, generally 12 which may
be rotatable at any desired speed, the robotic palletizer
generally ~4 and the film elevator generally 16 are the
major components. Several satellite components of a
preferred embodiment of the palletizer are also shown. A
pallet in~eed or supply conveyor 18 is located adjacent
the turntable and will serve a pallet to the turntable on
demand. Once a pallet is fully loaded and wrapped the
pallet will be shuttled to the pallet discharge conveyor
20. Product infeed is directed to the palletizer by
means of the product conveyor 22.
As stated earliee in this specification the
apparatus is contemplated as being able to stack and wrap
articles on alternate surfaces such as "pull sheets",
base sheets, low sided boxes and the like or even
directly on the surface of the turntable. A preferred
embodiment may include stacking on a conventional pallet
however equally good utility can be realized when using
the apparatus to stack and wrap on alternatives such as
the surface of the turntable.
In the event that a conventional pallet is not being
used it would be appropriate to eliminate, if so desired,
the pallet supply conveyor and possibly the output
conveyor.
Logically, starting with the product conveyor 22, a
metering infeed conveyor 24 will be the first element of
the palletizer opera-tion encountered by an article or
package such as 25 to ~e palletized, The pacXage, box
means, or article such as 2s could be of any
configuration that is stacked for shipment or storage on
a pallet, pull sheet or the like or the surface of the
turntable. Typically the box means 25 could be a box,
can, carton, open top carton, tray of material, nested
elements such as buckets, or even sacks or bags of
material, containers or pouches. The term "box means" is
not intended to be limiting and is used as a generic for
stackable materials beiny stacked together. For
readability of this specification the "box meansl' will be
referred to as "boxes" or its derivatives.
The metering infeed conveyor 24 may be equipped with
a rough surface top belt to provide separation between
131 1 1~6
5 ~
boxes as it delivers the boxes to the product conveyor
22~ Boxes may be aligned to one side of the metering
infeed con~eyor by an adjustable rail guide (not shown).
The product conveyor, also known as a station conveyor or
input station means, is a live roller assembly in a
preferred embodiment. Two or more photoeye sets are used
on this conveyor. Each set 26 a and b and 28 a and b
consists of a source/receiver component, the "a"
components, and a reflector, the "b" components, which
reflect the light from the source back to the receivers.
This is conventional technology. Various kypes of
sensors which may or may not require reflectors may be
used in place of the photoeye sets set out herein.
Throughout this specification photoeyes and reflectors
are discussed however these are simply one means of
sensing contemplated by the inventor. The first photoeye
set 26 is used to count boxes entering the station
conveyor. The second photoeye set is used to detect when
the last of a set of boxes 34 has accumulated on the
station conveyor.
The "set of boxes" 34 is that quantity of boxes that
should be accumulated before they are picked up by the
robotic palletizer and transferred to the turntable
generally 12. A set of boxes 34 would be, for instance,
the four boxes in contact with each other on the station
conveyor.
A case stop, which stops the boxes on the conveyor
is shown as 30. Other case stops, not shown, may be
positioned below the roller bed and activated as
necessary to interpose gaps between the boxes being
accumulated.
Once a set of boxes 34 is accumulated the robotic
palletizer can transfer them to an awaiting pallet on -the
turntable 12. Any incoming upstream boxes not necessary
to complete a set of boxes will be stopped until the full
set of boxes has been picked up by the robotic palletizer
and clears the station conveyor.
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In a normal cycle a pallet 3~, or -the equivalent of
a pallet such as a skid, "pull sheet," base sheet
platform, container means or the like, will be in
position on the turntable. Obviously, in the event tha~
a unitized load is to be built without a pallet or base
sheet no pallet or the like need be in position. The set
of boxes 34 will now be lifted by the grasping means 36
which may have any one of numerous -types of "hands".
Figure 1 shows the use of "palms" 38, two of which, an
inboard palm and an outboard palm have been marked as
38. One of the palms are stationary and the other of the
palms may be operated by an air cylinder (or other
closing or actuating means) to move toward the set of
bcxes 34 and clamp or grasp them between the palms,
"Hand" type is determined by ~pplication and a myriad of
hand types, including multiple palms bottom support
hands, vacuum, and top and bottom clamping, and the like,
are known in the industry. The hand may also be
articulated or movable on its support on an axis
perpendicular to the boom axis.
The structure of the grasping means 36 is carried
through cam rollers to a boom 40. The rollers of the
grasping means ride on and, in the case of the upper
rail, rails 42 and 44 so that the grasping means 36 can
traverse laterally from a location above the station
conveyor 22 to a specific discharge location on the
pallet on the turntable 12.
The boom 40 is slidably mounted on the mast 46 so
that the boom can move vertically on the mast. In a
typical "pick-and-place" the two axis provided by the
mast and the boom would be sufficient to transfer boxes
or sets of boxes from the station conveyor 22 to the
pallet 32. The operation proceeds as follows: The hand
36, poised above the set of boxes 34, is lowered, the
hand clamps causing the palms to grip the set of boxes,
the boom raises on the mast, the grasping means ~6 moves
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along the boom 40, the boom 40 moves down the mast 46,
the hand opens depositing the set of boxes 34 on the
pallet in a predetermined location. To return to star-t
the palms of the grasping means 36 are opened away from
each other, the boom raises away from the pallet, the
grasping means 36 moves back along the boom 40, the boom
moves down the mast 46 and the grasping means is ready to
grasp another set of boxes. The palletizer is programmed
to initiate movement, travel, change speed and find the
proper position for palletizing the sets of boxes in the
predetermined desired stacklng pattern.
After a palletized load has been partially "built",
that is stacked in a predetermined pattern, the partially
palletized load can be partially wrapped with film to add
stability to the partially palletized load. The stacking
pattern has traditionally been one that seeks to maximize
the number of boxes on the host pallet while interlocking
the boxes to help in palletized load stability and
integrity. Oftentimes this requires that certain boxes
be aligned along one axis of the pallet and the other
boxes are aligned along a second axis. On the next level
or layer of boxes the boxes will be aligned in opposite
dire~tions so that a certain amount of interlocking will
take place. Seldom are boxes stacked in vertical columns
by today's palletizers. Although the column strength is
much better when boxes are stacked directly on top of
each other as the boxes can be arranged so that the
strongest parts of the boxes, the corners, are stacked on
top of each other from box to box, the resulting tall
column is very unstable and all but unusable in
practice. The ins-tant invention however does provide for
effective column stacking and thus the apparatus of this
invention can provide a much more stable and strong
palletized loads than have been possible in the past.
Once a partial pallet load has been stacked on a
pallet, or a pallet means; in a preferred embodiment a
partial pallet load could be as few as two layers of
131 1 1~6
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boxes (wrapping can be done after only a single layer of
boxes has been stacked on the pallet however this would
not be a preferred embodiment); the wrapping operation
will be initiated by the controller for the palletizer.
Wrap means, usually a plastic film that has high
hysteresis after initial stretching, conventionally known
as "stretch wrap" film, is the preferred wrap means for
carrying out the intended purpose and operation of this
equipment.
Wrap means can be other types of film such as shrink
wrap film, polymer film, perforated film, netting, coated
or uncoated paper, ribbon, protective covers such as
bubble pack, and other covering materials or the like.
For convenlence the wrap means has been and will be
referred to as "film" in the disclosure.
The film, shown as a roll of film 48 is carried by
the film elevator generally 16 (wrap means unwind or film
dispensing unit) which is slideably mounted on a vertical
track 50. A chain hoist is used to raise the film
elevator. The chain 52 is attached to the f ilm elevator
at both ends and passes around a drive motor (not shown)
which is inside the vertical track support 54 for
convenience. The film is threaded (see Figure 3 from the
film roll 48 around a first main drive roller 56 then
around a second main drive roller 58. These two rollers
induce a significant amount of tension on the film
(called "pre-stretch"). The film then passes dancer
roller 60 which is movably mounted to control the speed
of drive of the main drive rollers 56 and 58 allowing -the
speed of the main drive rollers to increase as film
consumption is increased and decrease as film consumption
ls decreased. The film 6~, after leaving the pre
stretchhead generally 16, then passes over a guide roller
64, a first guide arm roller 66 and a second guide arm
roller 68, both of which are mounted on a film guide arm
70. The film then is directed to the wrap means clamp or
131 1 18~
g
film clamp 72 which is mounted on the turntable generally
12.
The film guide arm 70 serves to direct the film
around the mast 46 and to the film clamp 72 mounted on
the turntable generally 12. In a preferred embodiment
the film guide arm is held in a fixed position but may be
pivotally mounted for swinging movement about its
attachment point to the ilm elevator generally 16. If
the guide arm is pivotally mounted resistance to swinging
lo by means of a spring, air cylinder or like may be
advantageous in maintaining film tension to the film
clamp 72.
In an alternative embodiment a pivotally mounted
guide arm, being actuated by a motor of any type, by
gravity or by springs, would be programmed to be biased
from a first position to a second position to maintain
tension in the film specifically when the film would
normally have to be stretched and then released. By
providing a pivoting mounted guide arm the amount of
stretching and subsequent relaxation of the film could be
controlled and minimized. Returning again to a
description of the preferred embodiment, the height of
the guide arm and the length of the guide arm rollers is
of sufficient length or height to accept the width of
25 film being let off the film unwind. Typically film can
be about twerlty inches wide however wrap means wider or
more narrow ~han twenty inches is also commonly used. It
would not be unusual to use film that is as wide (or
wider than) as forty inches or as narrow (or more narrow
~han) ten inches.
The plan views presented in Figures 2, 3 and 4 have
been presented to assist in providing an understanding of
the apparatus.
In Figure 2, for instance, the turntable generally
12 is shown with at least a partial load of boxes 25
already in place. The mast 46, boom 40, grasping means
36, product conveyor 22 (the rollers have been left out
131 ~ 186
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of these views for simplicity), the film elevator,
generally 16, are each shown pictorially. Also the
pallet infeed conveyor 18 and the pallet discharge
conveyor 20, are shown with an empty pallet 32 and a
fully palletized load 33 orl the respective infeed and
discharge conveyors respectively. The significant items
that are more easily seen and understood in Figure 2 than
in Figure 1 include the "line of sight" paths of the
third photoeye set 74a and b, the pallet sensing photoeye
set 98a and b. Also the preferred brush 92 position is
shown in the solid line rendering of the securing means
while an alternative position 92A, wherein if the brush
were pivotally mounted to retract and move into the load,
is shown in the broken line presentation.
As stated elsewhere in this disclosure, the pallet
sensing photoeye set 98 is a conventional photoeye having
an integral beam emitter and receiver represented as 98a
and a reflector represented as 98b which will reflect the
beam back to the receiver unless a pallet (or other item)
blocks the light beam. When the beam is blocked the
palletizer controller knows that a pallet is in position
and the controller can initiate box stacking on the
pallet. When a pull sheet or base sheet is the surface
on which boxes will be stacked the photoeye set 98 may be
2s replaced with a reflective photoeye sensing system or a
manual or automatic switch or the like providing a signal
to the controller that it can begin stacking boxes. It
should also be realized that boxes can be stacked
directly on the turntable surface for transport by a
"palm" truck or if so desired.
The third photoeye set 74a and b can be seen in this
Figure as well. This photoeye set senses the top of a
layer of boxes. This input is used by the controller to
control the vertical upward limit of the film elevator
generally 16.
Figures 2 and 3 also show the film path :Erom the
film elevator 16 to the film clamp 72. In Figure 3 the
131 1 186
roll of film 48, from which film 62 is unwound is shown
in a pictorial plan view. The film 62 is threaded around
first and second main drive rolls 56 and 58, which are
driven at a speed differential in a preferred embodiment
in order to prestretch the film, then around a dancer
roller 60 and a guide roller 64. The film then passes
over first and second guide arm rollers 66 and 6a and
then to the film clamp 72 which is shown in the "home"
position (far the preferred embodiment) in all the
Figures except Figures 4 and 5.
In Figures 4 and 5 intermediate stages of a typical
stacki~g and wrapping cycle are shown. In Figure 4 a
wra~ cycle has been initiated and the turntable has
rotated clockwise 90, for example, on a first wrap
cycle. The film 62 is held fast in the film clamp 72 and
the film is seen to be in contact with the corner of the
stack of boxes on the turntable. Upon the turntable
reaching the home position one wrap of the stack of boxes
will have been made. The cycle will continue as
explained i~ this disclosure.
In Figure 5 the loading or positioning of an empty
pallet is shown. Since the film clamp 72 will normally
be upstanding at the completion of the wrapping of a full
load and will be in the "home" position shown in Figure 2
it is necessary to get the film clamp (and the film 62)
out of the path of the pallet 32 as it is being loaded.
One way to do this is to rotate the turntable
counterclockwise 90 as shown in this figure. It should
be noticed that film 62 is taut when the film clamp is in
the position shown in the Fi.gure. The pallet sensing
photoeye 98a will have its beam broken when the pallet 32
moves further into position on the turntable.
A wrapping cycle Of a preferred embodiment
palletizer represented by Figure 1 will be initiated by
the palletizer controller when a signal is received by
~he palletizer tha-t the height of boxes desired far the
first wrap cycle has been achieved. Good machine
131 1 1~6
performance and stack integrity is achieved if the first
wrap cycle is performed after two layers of boxes have
been positioned.
In the first wrap cycle the film is being held
clamped in the film clamp 72. The grasping means 36 has
been cycled away from the partially stacked pallet and
continues to cycle to pick up the next set of boxes while
the first wrap cycle is being performed. The turntable
generally 12 is rotated clockwise from a home position
~from above), generally the zero and three hundred sixty
degree position in this preferred embodiment, causing
film to be pulled off the roll of film 48. Close in
timing to the initiation of turntable rotation, that is
either before, after, or simultaneously therewith, the
film elevator generally 16 has been signaled by the
palletizer controller to move vertically upward on the
vertical tracX 50. Such upward movement of the film
elevator will the lower switch 78 to open. Upward
movement of the film elevator causes the film to be
spiralled up the stack of boxes on the pallet as the
turntable continues its rotation. The film is now being
wrapped around the stack while still being held by the
film clamp 72,
This first wrap cycle will continue until the
palletizer senses that the top of the top layer of boxes
has been reached. Generally, the first wrap cycle is
accomplished in one 360 rotation Of the turntable,
however more than one rotation may be bene~icial in some
applications. The signal, signifyin~ that the top layer
of boxes has been reached, will come from photoeye three
74a which sends a beam of light to a reflector 74b
mounted on a vertical support or reflector pale. The
reflector 74b is a continuous reflector of significant
length mounted on the reflector pole whose length is
sufficient to accommodate boxes of different heights.
When the photoeye sensor 72a senses the top of the boxes
it will signal the palletizer controller to signal the
131 1 186
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film elevator drive to stop elevating the film elevator.
At this point the turntable will continue rotating until
it has returned to its home position. The film clamp 72
maintains the film in its clamped position.
Although the film elevator will normally be set to
stop its upward travel at a point where the film does not
go above the top of the boxes on the pallet it may be
advantageous in some cases to allow the film elevator to
go higher. If, for instance, the film elevator goes to a
point such that the film is two inches higher than the
top surface of the boxes the film will be stretched to be
drawn inboard of the outer edges of the boxes. This may
be advantageous, in stabilizing the stack, if the
following set of boxes is then placed on this inwardly
directed portion of the film.
Upon the turntable returning to the home position
the stacking unit will commence stacking more layers of
boxes on the pallet. It will stack, for instance,
another two layers o~ produc-t and signal the commencement
of the wrapping cycle. The second and subsequent
wrapping cycles will be, in a preferred embodiment,
repeats of the first wrapping cycle until the full height
of the palletized load is achieved - full height being
the number of layers of boxes that have been
preprogrammed into the palletizer controller.
When a fully stacked load has been accumulated on
the turntable the top of the boxes of the top layer are
sensed by the third photoeye set 74 and the film elevator
will stop elevating the film roll to prevent the film
from going off the top of the stack. This is the same as
the sensing of the prior spiral wrap cycles.
As earlier pointed out in discussing the completion
of the first wrap cycle it is possible to extend the film
somewhat higher than the top of the top layer of boxes in
order to provide some further unitizing assistance to the
full load of stacked articles. The film elevator can be
programmed to go slightly higher than the top of the
131 1 1~36
boxes either immediately or internally ~o possible
multiple wraps at the top of the stack.
Once the spiral wrap has been applied to the fully
palletized load a unifying wrapping of the palle~ized
load would be desirable to further unitize, strengthen
and build integration into the palletized load. While
the spiral wrapping accomplished in the first and several
subsequent wrapping cycles serves to unify and help
support the load as it is being stacked, allowing by the
way, the building of a load of column stacked boxes among
other advantages, it may or may not be as complete a
wrapping job as desirable for insuring integ,ation of the
palletized load.
It may be desirable, as an alternative, to do all
the wrapping of the pallet load as the stack is being
formed. In this case instead of just spiral wrapping on
the way up the controller would direct the unwrapping
head to stay at a horizontal position while the turntable
made a single or a number sf revolutions to wrap the
stack at that level. This could be done at various
heights on the stack as it is being built. This would
lessen the time to wrap after the load has been stacked
as some of this wrapping could be in-ternal to the
"picking" of the stacker.
Further wrapping, of the preferred embodiment style
of the invention and if desired would be completed as
follows. With the film elevator high on the vertical
track 50 and 5ignaled not to go any higher by the
photoeye set 74, the palletizer controller signals the
turntable to make at least one full revolution, three
revolutions works well, while the film elevator is held
in its position relative to the top of the palletized
load. After the desired number of revolutions have
applied a "top wrap" and if desired the film elevator is
signaled to let the film elevator travel down the
vertical track 50 at a controlled rate while the
palletized load continues to rotate. The film elevator
1 3 1 1 1 g6
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may be directed to hold its horizontal position or to
decline at a slow rate to apply more film at designated
heights of the palletized load or it may continue to
travel downwardly thus spiral wrapping the palletized
load during its travel.
A sensor or intermediate switch 76, typically a
micro switch or the like, will signal the palletizer
controller when the lower portion of the film elevator is
just above the top of the film clamp 72 - which at this
point in the cycle is still clamped to the leading edge
of the film.
When this intermediate switch 76 is "made" the
palletizer controller signals the film clamp to retract
and let the leading edge of the film hang free. With the
~ilm clamp retracted to a position typically below the
bottom of the first layer of boxes the film elevator
generally 16 can continue its downward travel and wrap
the bottom portion of the palletized load with several
layers of film through several rotations of the turn-table.
A variation of the first spiral wrap cycle or the
first or second rotation of the full top wrap cycle would
be to allow the film wrapper to position a portion of the
film, on the order of several inches, more or less,
depending on the stretch quantities of the stretch wrap
film above the top of the top edge of the top layer of
boxes. This could create a degree of improved integrity
in some types of stac~ed products.
It would be possible to use this technique at the
intermediate stages of the spiral wrapping operation
however such technique is not the most preferred
embodiment.
In some situations it is desirable to have the film
extend over the supporting pallet, low box or the like on
which the articles are stacked. This provides continuity
between the supporting pallet and the articles so that
the articles and the pallet are somewhat packaged
together. This is not always necessary or desirable.
- 16 -
Returning to the completion of the cycle, th~
leading edge o~ the fi lm has been rapidly covered, at
least partially by the film being wrapped on the
palletized load as the film elevator goes to the lower
section of the load. Although the leading edge of film
is rapidly covered through rapid rotation of the
turntable, it has been found that a stream of air
directed at the loose leading edge of the film is
advantageous in holding the leading edge of the film
against the load until the film can be overlayed with
subsequent wraps of ~ilm. An air nozzle 76, which
receives air from an air supply (not shown) provided to
the turntable, is mounted on the turntable to accomplish
this function.
On the final revolution of the turntable after the
desired number of wraps or revolutions have been made it
is necessary to position the film in the film clamp in
preparation for the next palletizing operation. This is
done in the final one hundred eighty degrees of
revolution of the turntable. The film clamps are in a
retracted deployment at the start of the clamping cycle.
After the turntable has rotated one hundred eighty
degrees on its final rotation a signal is sent to the
palletizer controller to deploy the trailing element 84
of the film clamp. It should be pointed out that the
film clamp 72 is made up of two major clamping elements.
These are the leading element 82 and the trailing element
84. The leading element is a structural member having a
grip enhancing surface such as a rubber coating along its
film engaging surface. The trailing element 84 also is a
structural member with a grip enhancing surface. When
film is positioned between the leading and trailing
elements it is held fast until the film clamp is opened
(just before the film elevator 16 interfaces with the
upright film clamp 72).
Once the trailing element 84 has been deployed into
an upstanding position - the leading element is still in
131 1 1~6
- 17 -
a retracted or generally horizontal position - the
continued rotation of the tur~table will cause the
trailing element 84 to contact the film between the
palletized load and the film guide arm 70. The turntable
continues its rotation and during this continued rotation
the leading element of the film clamp is deployed into a
position to clamp the film between the leading and
trailing elements of the film clamp.
At this point the film is clamped in the film clamp
but is still attached in a continuous sheet to the fully
wrapped palletized load. To sever the film it has been
found that a heated rod pivoted across the film path will
cleanly cut the film. Such a heated rod film terminator
or cutter is shown as 86 in a retracted position on the
turntable. The heated rod is carried on a support that
is pivotatally mounted at one end and is further
actutable by an air cylinder (not shown).
Once the film is severed by the heated rod or other
film terminating means such as a hot wire, a knife, or
the like, the palletized load is completed and it can be
moved off the turntable.
In a preferred embodiment the turntable has a
powered roller deck surface 88 that can discharge the
palletized load to a pallet discharge conveyor generally
20.
However the palletized load is removed from the
turntable it has been found that in some applications it
is desirable to "pat down" or smooth over the trailing
end of the film to remove trapped air for better tail
adhesion to the load. This trailing film end is normally
stuck to the film on the palletized load since it
"springs back" somewhat after being cut by the heated
knife 86. Nevertheless an optional step in the method of
palletizing discussed here is to "pat down" the end of
the film through the use of a securing means 9o. The
securing means shown in Figure 1 is a brush 92 supported
on a stan-tion 94 and having a drive means 96 for rotating
I;~1 I I~6
- 18 -
the brush 92 as the pallet moves from the turntable to
the pallet discharge conveyor 20. The brush may be
spring loaded to be urged against the palletized load in
the proximity of the trailin~ end of the film to thereby
pat down the trailing end to the film below it on the
pallet. The securing means can be any of several types
o~ devices such as a soft surfaced or hard surfaced
roller, a blast of air directed to the film trailing end,
a stationary ramp that applies pressure to the film tail
as it is delivered to the pallet discharge conveyor, or
the like.
In situations such as shown by Figure 5 where the
film 62 will "go slack" as the turntable is rotated
counterclockwise and then get taut again as the film
clamp 72 gets to the 90 position shown it has been found
to be advantageous to control the amount of prestretch
exerted on the film by the prestretch rolls, these being
the first 56 and second 58 main drive rolls so that film
is not payed out unnecessarily.
Figure 6 is a chart that shows how the rolls 56 and
58 are turned off and on to assure that excess film is
not fed. It should be ~oted that the drive rolls 56 and
58 are turned "on", stripping film from the film roll 48
in response to dancer roller 60, which is free to move
inboard as shown by the arrow in Figure 3, when more film
is needed. This is contemporary film unwind practice.
sut when using prestretch ~ilm the ~ilm will, a~ter being
initially prestretched between rollers 56 and s8,
"recover~ causi~g dancer roller 60 to be pulled inboard
and initiate driving feed by the rollers 56 and 58. This
will happen to a controlled degree whenever the film is
not being wrapped on the boxes - typically when the
turntable is in the home position.
The Figure 6 chart shows how the pres~retch unit is
Shut off or turned on on the final revolution of the wrap
cycle and the reversing of the turntable to allow the
pallet to be loaded. The controller is given signals
t31 1 186
- 19 -
from limit switches that are placed to pick up turntable
posi~ion.
Starting at point A and progressing to B (arrowheads
indicate direction of turntable travel) ~he film
prestretch unit is "on", that is it is operative to feed
film during this final revolution of the load and
turntable. At point B approximately 330 of rotation the
prestretch unit is turned off ceasing the possibility of
feeding of film (B, to C). From C, to D the turntable is
moving counterclockwise to approximately 270 as shown in
Figure 5 - prestretch unit is off. After the pallet is
loaded the turntable rotates clockwise and at
approximately 330 (D, to E, prestretch unit is off) the
prestretch unit is turned on for the duration of the
revolution (E, to F).
Figures 2A through 2F have been provided to show
layouts of ancillary services to the palletizer. The
principals of operation of these alternative layouts will
be the same as the embodiment shown in Figure 1 for the
most part.
Figure 2A is simply the reverse of the Figure 1, 2
structure such that product infeed is on the left side of
the turntable (reference point is from mast in direction
of boom).
Figure 2B has a pallet infeed conveyor 104 entering
the turntable from the right of the turntable. In this
embodiment the product conveyor 22 may be elevated to
allow pallets to be served underneath it. In this layout
the turntable may have to be rotated counterclockwise
such that the film clamp 72 will not interfere with the
loaded pallet being unloaded from the turntable to the
pallet discharge conveyor 20.
Figure 2C is simply the reverse of the Figure 2B
layout.
Figure 2D is similar to Figure 2 except that the
positions of the pallet infeed or supply conveyor 18 has
1 ~1 1 1 ~6
- 20 -
taken the place o~ the pallet discharge conveyor 20 and
vice-versa.
Figure 2E is simply the reverse of the Figure 2D
layout.
Figure 2F is a palletizer with no pallet infeed or
discharge conveyor. The palletizer tu~ntable 12 will be
serviced by transport means such as a forklift truck or a
pull sheet handling vehicle.
Figure 7 shows an alternative embodiment of the
invention specifically directed to the use of a short
film clamp 100. All other aspects of this embodiment are
the same as shown in Figur~ 1 with the exception of the
short film clamp lO0, the added film roping roller 102
and the repositioning of the lower switch 78 to a
position lower on its support than the position of the
switch in the Figure 1 embodiment.
In this embodiment the film clamp 100 is shorter
than the width of the film 62. The film 62 is thus
"roped down" as shown to fit into the jaws of the film
clamp. The film elevator 16 has dropped so low on the
ver-tical track 50, due to the low position of the limit
switch 78, that the film would foul on the upper surface
of the turntable. The roping roller 102 guides the film
above the turntable surface and as it does it tends to
"rope down" the film. The advantage o~ the shorter f ilm
clamp 100 is that on the initial wraps of the lower
levels of boxes the film elevator doesn't have to be
lifted as high to clear the short film clamp as it would
if there were a taller film clamp (Figure 1) being used.
ThiS allows wrapping more Of the lower level of the
stacked boxes whiCh may be advantageous for some loads.
This disclosure has atternpted to set forth a
description of apparatus that can stack and unitize a
collection of articles into a unified package. Although
several modes of carr,,ving out the invention, including a
best mode known to the inventors, ha~e been disclosed it
is contemplated that nuances of design and engineering
131 1 186
- 21 -
expedlancies may be utilized in the deslgn of a uni~izing
wrapper. Such nuances and expediancies are contemplated
by the inventors and are sought to be covered by the
following claims.
