U.S. patent application number 10/159282 was filed with the patent office on 2002-11-21 for method of and apparatus for depalletizing commodities.
Invention is credited to Donner, Knut, Hoppe, Hans-Jurgen, Keil, Uwe.
Application Number | 20020172586 10/159282 |
Document ID | / |
Family ID | 7815968 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020172586 |
Kind Code |
A1 |
Donner, Knut ; et
al. |
November 21, 2002 |
Method of and apparatus for depalletizing commodities
Abstract
Successive palletized stacks of blanks in a layer of such stacks
on a penetrable support of cardboard or the like are lifted off the
support by a substantially horizontal plate- or blade-like
implement which is caused to penetrate between the upper side of
the support and the underside of a selected stack prior to lifting
of the selected stack off the support for transfer onto a conveyor
or into a blank converting machine, such as a cigarette packing
machine. An optical or other suitable monitoring unit has one or
more sensors which share the movements of the implement to detect,
and to effect the generation of defect signals in response to the
detection of, improper operation of the apparatus, such as the
penetration of the implement through and subsequent lifting of a
portion of the support with a selected stack.
Inventors: |
Donner, Knut; (Hamburg,
DE) ; Hoppe, Hans-Jurgen; (Epenwohrden, DE) ;
Keil, Uwe; (Schwarzenbek, DE) |
Correspondence
Address: |
VENABLE, BAETJER, HOWARD AND CIVILETTI, LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Family ID: |
7815968 |
Appl. No.: |
10/159282 |
Filed: |
June 3, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10159282 |
Jun 3, 2002 |
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09616369 |
Jul 13, 2000 |
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09616369 |
Jul 13, 2000 |
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08974389 |
Nov 19, 1997 |
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6332750 |
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Current U.S.
Class: |
414/796.9 ;
414/796 |
Current CPC
Class: |
B65H 3/325 20130101;
B65G 59/023 20130101 |
Class at
Publication: |
414/796.9 ;
414/796 |
International
Class: |
B65G 059/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 1996 |
DE |
196 53 953.6 |
Claims
What is claimed is:
1. A method of removing a commodity from an upper side of a support
by means of an apparatus which includes a substantially horizontal
lifting implement movable in a plurality of directions including
downwardly toward, upwardly away from and along the upper side of
the support, comprising the steps of introducing the implement
between the commodity and the upper side of the support; monitoring
the position of at least one of the implement, the support and the
commodity not later than upon completion of said introducing step
and generating a signal at least when the monitored position
departs from a predetermined position; and moving the implement and
the commodity relative to and away from the support at least when
the monitoring step does not result in the generation of a signal
denoting that the monitored position departs from the predetermined
position.
2. The method of claim 1, wherein the commodity comprises at least
one stack of superimposed substantially flat blanks.
3. The method of claim 1, wherein said monitoring step is carried
out at least in the course of said introducing step.
4. The method of claim 1, wherein said monitoring step is carried
out upon completion of said introducing step.
5. The method of claim 1, wherein said signal is a defect signal,
and further comprising the step of blocking said moving step in
response to the generation of a defect signal.
6. The method of claim 5, further comprising the step of correcting
the monitored position in response to the generation of a defect
signal.
7. The method of claim 1, wherein said introducing step includes
moving the implement dowardly at least close to the upper side of
the support adjacent the commodity and thereupon advancing the
implement along the upper side between the commodity and the upper
side of the support.
8. The method of claim 1, further comprising the step of lifting at
least a portion of the implement and of the commodity above and
normally away from the upper side of the support subsequent to said
introducing step and prior to said monitoring step.
9. The method of claim 8, wherein said monitoring step includes
monitoring the position of the support.
10. The method of claim 9, wherein said signal is generated when
said monitoring step reveals a lifting of at least a portion of the
support with said portions of the commodity and the implement.
11. The method of claim 9, wherein said lifting step includes
lifting portions of the commoditiy and of the implement through a
distance in the range of approximately 10 mm.
12. The method of claim 9, wherein said monitoring step includes
optically scanning the position of the support.
13. The method of claim 9, wherein said monitoring step includes
mechanically scanning the position of the support.
14. The method of claim 9, wherein said monitoring step includes
the utilization of a fluid-operated monitoring device.
15. Apparatus for removing commodities from an upper side of a
support, comprising a displacing unit including a substantially
horizontal lifting implement and means for moving said implement in
a plurality of directions including downwardly toward, upwardly
away from and along the upper side of the support so that the
implement can be introduced between the upper side of the support
and a selected commodity at the upper side; means for monitoring
the position of at least one of said implement, the support and the
selected commodity not later than upon completion of introduction
of the implement between the upper side of the support and the
selected commodity, including means for generating signals denoting
the monitored position; and means for evaluating said signals.
16. The apparatus of claim 15, wherein said generating means is
arranged to generate defect signals when the monitored position
departs from a predetermined position, said moving means being
operative to move said implement and the selected commodity away
from the upper side of the support at least in the absence of
generation of a defect signal.
17. The apparatus of claim 15, wherein said monitoring means
includes means for monitoring the position of the support.
18. The apparatus of claim 17, wherein said monitoring means
comprises a position sensor carried by said moving means and
extending toward the upper side of the support.
19. The apparatus of claim 18, wherein said signals denote the
position of the support beneath said implement.
20. The apparatus of claim 15, wherein said monitoring means
includes an optical sensor for the position of the support, said
sensor being borne by said moving means.
21. The apparatus of claim 20, wherein the upper side of the
support reflects radiation and said sensor includes a source of
radiation and means for directing radiation from said source
against the upper side of the support, said signal generating means
being operative to generate signals denoting the characteristics of
radiation being reflected by the upper side of the support.
22. The apparatus of claim 15, wherein said moving means includes
means for moving at least a portion of said implement and at least
a portion of the selected commodity upwardly to predetermined
positions upon introduction of said implement between the upper
side of the support and the selected commodity, said monitoring
means including means for monitoring the position of the support in
said predetermined positions of said portion of said implement and
said portion of the selected commodity and said signal generating
means being arranged to transmit to said evaluating means a signal
denoting the monitored position of the support in said
predetermined positions of said portions of said implement and the
selected commmodity.
23. The apparatus of claim 15, wherein said monitoring means is
borne by said moving means and includes a mechanical sensor
constituting said signal generating means.
24. The apparatus of claim 15, wherein said monitoring means is
borne by said moving means and includes a fluid operated sensor
constituting said signal generating means.
25. The apparatus of claim 24, wherein said sensor is a pneumatic
sensor.
26. The apparatus of claim 24, wherein said sensor includes a
dynamic pressure transducer.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to improvements in methods of an in
apparatus for temporarily storing commodities and for removing,
when necessary, commodities from storage. More particularly, the
invention relates to improvements in methods of and in apparatus
for removing (depalletizing) commodities from temporary storage
facilities in the form of pallets. Typical examples of commodities
which can be manipulated in accordance with the improved method and
with or by the improved apparatus are stacks of superimposed
articles, e.g., flat or substantially flat blanks of paper,
cardboard, plastic material and/or metallic foil which are designed
for conversion into containers or receptacles (such as packets) for
arrays of plain or filter cigarettes or other articles or products
of the tobacco processing industry. Still more particularly, the
invention relates to improvements in methods of and in apparatus
for depalletizing commodities which are temporarily deposited on
normally at least slightly deformable and/or penetrable supports in
the form of sheets, tarpaulins or panels which are placed between
superimposed layers of commodities on pallets or analogous
conveyances.
[0002] Depalletizing apparatus of the category of apparatus to
which the present invention pertains are disclosed in European
patents Nos. 0 532 949 A1, 0 363 722 B2 and 0 354 873 B1. The
patented apparatus are designed to singularize accumulations of
blanks which are stacked on pallets and are to be fed to packing
machines, such as cigarette packing machines, for conversion into
portions of or into entire packets, e.g., into packets each of
which is dimensioned and configurated to accept and confine an
array of twenty plain or filter cigarettes in the customary
quincunx formation.
[0003] A modern high-speed cigarette packing machine (or another
blank processing or converting machine) is designed to turn out
huge quantities of packaged products per unit of time. Thus, even a
relatively short interruption of the feed of blanks to such a
machine can entail enormous losses in output. Therefore, such
machines are often combined with a conveyor system which employs
mobile pallets capable of temporarily storing numerous stacks of
superimposed blanks, preferably in a distribution to afford
convenient access to the stacks in a given sequence and unimpeded
transfer into one or more blank-receiving magazines of a packing
machine.
[0004] As mentioned above, it is already known to employ pallets
which are designed to temporarily receive and transport large
numbers of stacks of superimposed blanks made of paper, cardboard
and/or other material or materials, often in the form of several
superimposed layers which are separated from each other by
sheet-like or analogous supports and each of which can contain a
plurality (e.g., several dozens) of coplanar stacks. For example,
the supports between neighboring superimposed layers of stacks of
paper or cardboard blanks can be made of cardboard or a sheet- or
panel-like material of similar consistency, and a pallet can
support a substantial number of layers with supports (e.g., six
cardboard panels) between neighboring layers.
[0005] Certain presently known depalletizing apparatus employ a
tool or implement which is movable in several directions so that it
can be caused to penetrate between the upper side of a topmost (or
the only) support and the underside of a selected stack on such
topmost or only support. The next step involves a lifting of the
selected stack above and away from the upper side of the support
and the transfer of the thus lifted stack onto a suitable conveyor
which delivers the stacks into the blank-receiving magazine of a
packing machine. As a rule, and in order to facilitate and simplify
the introduction of the implement between the upper side of a
support and the underside of a selected stack on such support, the
implement is borne by a drive which can move the implement in the
direction of the X, Y and Z axes, namely up and down (Z axis) as
well as in a horizontal plane in two directions (X and Y axes)
extending at right angles to each other. Once the implement has
been moved to a required level (at the upper side of a support), it
is moved in the direction of the X or Y axis to penetrate between
the upper side of the support and the underside of the lowermost
blank in a selected stack.
[0006] Problems arise when the upper side of a support is not
smooth or is not flat or is slotted or otherwise damaged (e.g., as
a result of repeated use) so that the normally sharp or reasonably
sharp leading edge of the implement penetrates into and thereupon
lifts a portion of the support together with a selected stack above
it. This can result in undesirable shifting of one or more
neighboring stacks on the partially lifted support and/or in at
least some undesirable shifting (or complete collapse) of the stack
overlying the implement. In either event, the transfer of stacks
from the pallet must be interrupted for a certain interval of time
to permit for manual separation of the implement from the lifted
portion of the support as well as for the reestablishment of
orderly distribution, orientation and configuration of neighboring
stacks. This can entail huge losses in output, especially if the
impaling and lifting of a portion of a support is detected with a
certain delay. In many instances, an irregularity in the
depalletizing operation can be remedied only upon stoppage of an
entire production line, e.g., a production line embodying one or
more cigarette rod makers, one or more filter tipping machines and
one or more packing machines.
OBJECTS OF THE INVENTION
[0007] An object of the invention is to provide a novel and
improved method of depalletizing stacks of superimposed blanks or
other types of commodities in such a way that losses attributable
to improper removal of a commodity are reduced to a minimum.
[0008] Another object of the invention is to provide a method which
can be practiced with apparatus constituting relatively minor but
ingenious departures from conventional depalletizing apparatus.
[0009] A further object of the invention is to provide a method
which, though especially suitable for the practice in connection
with the manipulation of paper, cardboard or other blanks which are
to be converted into packets or other types of receptacles or
containers for smokers' products, can be resorted to with equal or
similar advantage for the depalletizing of many other types of
commodities which are to be manipulated in a highly predictable
fashion and with a minimum of supervision by and/or assistance from
attendants.
[0010] An additional object of the invention is to provide a novel
and improved depalletizing method which can be practiced by
resorting to simple, compact and relatively inexpensive apparatus
for predictable removal of commodities from available pallets
and/or supports.
[0011] Still another object of the invention is to provide a novel
and improved apparatus for the practice of the above outlined
method.
[0012] A further object of the invention is to provide the
apparatus with novel and improved means for rapidly and reliably
detecting irregularities in the depalletizing of stacks of blanks
or other types of commodities.
[0013] Another object of the invention is to provide a machine
which employs one or more depalletizing apparatus exhibiting the
above outlined features and advantages.
[0014] An additional object of the invention is to provide a novel
and improved combination of a mobile commodity manipulating
implement, means for moving the implement relative to commodities
on a pallet, and means for detecting and indicating the detection
of irregularities in the depalletizing of commodities.
[0015] Still another object of the invention is to provide novel
and improved methods and apparatus for feeding accumulations of
paper, cardboard or other blanks to one or more packing machines,
particularly to one or more machines for packing arrays of plain or
filter cigarettes or other smokers' products.
[0016] A further object of the invention is to provide a
depalletizing apparatus which requires less attention on the part
of one or more attendants than heretofore known depalletizing
apparatus.
[0017] Another object of the invention is to provide an apparatus
which is constructed, assembled and adapted to be operated in such
a way that the departures, if any, of its operation from an optimum
mode of operation can be remedied or eliminated within shorter
intervals of time than those of conventional apparatus, such as
those disclosed in the above-enumerated European patents.
SUMMARY OF THE INVENTION
[0018] One feature of the present invention resides in the
provision of a method of removing a commodity (such as a stack of
paper blanks or the like) from the upper side of a support by means
of an apparatus which includes a substantially horizontal lifting
implement movable in a plurality of directions including downwardly
toward, upwardly away from and along the upper side of the support.
The improved method comprises the steps of introducing the
implement between the commodity and the upper side of the support,
monitoring the position of at least one of the implement, the
support and the commodity not later than upon completion of the
introducing step and generating a signal at least when the
monitored position departs from a predetermined position, and
moving the implement and the commodity relative to and away from
the support at least when the monitoring step does not result in
the generation of a signal denoting that the monitored position
departs from the predetermined position.
[0019] As already mentioned above, the commodity can comprise at
least one stack of superimposed substantially flat blanks of paper,
cardboard, plastic material, metallic foil and/or others.
[0020] The monitoring step can be carried out at least in the
course of the introducing step or upon completion of the
introducing step.
[0021] The signal which is generated in the course of the
monitoring step can constitute a defect signal, and such method can
further comprise the step of blocking the moving step in response
to the generation of a defect signal. Such method can further
comprise the step of correcting (e.g., manually) the monitored
position in response to the generation of a defect signal.
[0022] The introducing step can include moving the implement
downwardly at least close to the upper side of the support adjacent
the commodity to be lifted off the support, and thereupon advancing
the implement along the upper side of the support to cause the
implement to enter between such upper side and the underside of the
commodity.
[0023] The method can further comprise the step of lifting at least
a portion of the implement and at least a portion of the commodity
above and normally away from the upper side of the support
subsequent to the introducing step and prior to or simultaneously
with the monitoring step. The monitoring step preferably includes
monitoring the position of the support. The signal can be generated
when the monitoring step reveals a lifting of at least a portion of
the support with the portions of the commodity and the implement.
The aforementioned lifting step can include lifting or raising
portions of the commodity and of the implement through a distance
in the range of several millimeters, e.g., in the range of
approximately 10 mm.
[0024] The monitoring step can include optically scanning the
position of the support. Alternatively or in addition to optical
scanning, the monitoring step can include mechanically,
hydraulically or pneumatically scanning the position of the
support.
[0025] Another feature of the invention resides in the provision of
an apparatus for removing commodities from the upper side of a
support. The improved apparatus comprises a displacing unit
including a substantially horizontal lifting implement and means
for moving the implement in a plurality of directions including
downwardly toward, upwardly away from and along the upper side of
the support so that the implement can be introduced between the
upper side of the support and a selected commodity at such upper
side, means for monitoring the position of at least one of the
implement, the support and the selected commodity not later than
upon completion of introduction of the implement between the upper
side of the support and the underside of the selected commodity
including means for generating signals denoting the monitored
position, and means for evaluating such signals.
[0026] The means for generating signals can be arranged to generate
defect signals when the monitored position of the implement and/or
selected commodity and/or support departs from a predetermined
position, and the moving means is preferably operative to move the
implement and the selected commodity away from the upper side of
the support at least in the absence of generation of a defect
signal.
[0027] In accordance with a presently preferred embodiment of the
invention, the monitoring means preferably includes means for
monitoring the position of the support. Such monitoring means can
comprise a position sensor which is carried by the moving means and
extends toward the upper side of the support. The arrangement can
be such that the signals denote the position of that portion of the
support which is located beneath the implement or beneath a portion
of the implement if the latter is permitted or caused to penetrate
into and through the support.
[0028] The monitoring means can include an optical sensor for the
position of the support, and such sensor is preferably borne by the
moving means for the implement. The material and/or the coating of
the support can be selected in such a way that its upper side
reflects radiation, and the optical sensor can include a source of
radiation and means for directing radiation from such source
against the upper side of the support. The signal generating means
of such monitoring means is operative to generate signals denoting
at least one characteristic (e.g., the intensity) of radiation
which is being reflected by the upper side of the support.
[0029] The moving means can include means for moving at least a
portion of the implement and at least a portion of the selected
commodity upwardly to predetermined positions subsequent to
introduction of the implement between the upper side of the support
and the underside of the selected commodity, and the monitoring
means of such apparatus can comprise means for monitoring the
position of the support in such predetermined positions of the
portion of the implement and portion of the selected commodity. The
signal generating means of such monitoring means is preferably
arranged to transmit to the evaluating means a signal denoting the
monitored position of the support in the predetermined positions of
the portions of the implement and the selected commodity.
[0030] The monitoring means is preferably borne by the means for
moving the implement and can include a mechanical and/or a
fluid-operated (hydraulic or pneumatic) sensor which constitutes or
forms part of the signal generating means. The fluid-operated
sensor can include a dynamic pressure transducer.
[0031] The novel features which are considered as characteristic of
the invention are set forth in particular in the appended claims.
The improved apparatus itself, however, both as to its construction
and its mode of operation, together with numerous additional
important and advantageous features thereof, will be best
understood upon perusal of the following detailed description of
certain presently preferred specific embodiments with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a perspective view of a pallet for temporary
storage of superimposed layers of commodities with the neighboring
layers separated from each other by sheet-like supports of
cardboard or the like in a manner for depalletizing in accordance
with the method and by resorting to the apparatus of the present
invention;
[0033] FIG. 2 is an elevational view of an apparatus which embodies
one form of the present invention and wherein the lifting implement
is held in a position preparatory to penetration between the upper
side of a support and the underside of a selected commodity;
and
[0034] FIG. 3 is a similar elevational view but showing the
implement and the selected commodity in partially lifted positions,
and further showing a portion of the support in an improper
position which the support assumes as a result of traversal by the
relatively sharp leading edge of the implement.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0035] FIG. 1 shows a standard pallet 1 which carries an array of
block-shaped commodities 2, e.g., stacks of superimposed at least
substantially flat blanks of paper, cardboard and/or other suitable
material. The blanks can be designed for conversion into packets
for plain or filter cigarettes if the pallet 1 is utilized in a
production line to temporarily store commodities 2 (hereinafter
called stacks for short) which are to be transferred into the
magazine(s) of one or more packing machines for rod-shaped articles
of the tobacco processing industry. However, it is to be understood
that the method and apparatus of the present invention can be
utilized for the manipulation (depalletizing) of other types of
commodities in machines or production lines which may but need not
necessarily be utilized in the tobacco processing industry.
[0036] The stacks 2 are arranged in several horizontal layers, and
each such layer rests on a sheet- or panel-like support 3, e.g., a
support made of cardboard or the like. The number of supports 3,
the number of layers of stacks 2, and the number of stacks 2 in
each layer can depart from those shown in FIG. 1. The manner in
which the palllet 1 can be loaded with layers of stacks 2 and with
supports 3 and/or the manner of transporting the pallets to and
from a depalletizing station form no part of the present invention.
The neighboring stacks 2 in the longitudinally and/or transversely
extending rows of stacks in a layer may but need not actually abut
each other. FIG. 1 shows that the longer sides of neighboring
stacks 2 in a layer are closely adjacent or actually abut each
other but the shorter sides of neighboring stacks are spaced apart
from one another.
[0037] The purpose of the supports 3 is to stabilize the layers of
stacks 2 as well as to stabilize the entire (multi-layer)
accumulation of stacks on the pallet 1.
[0038] One presently preferred apparatus (4) for depalletizing
accumulations of stacks 2 of the type shown in FIG. 1 is
illustrated in FIG. 2. The lower part of FIG. 2 shows a portion of
a single support 3 (such as the topmost support on the pallet 1 of
FIG. 1) and three stacks 2.1, 2.2 and 2.3. The stack 2.1 can be
said to constitute a selected stack or commodity because it is
about to be lifted off the upper side of the support 3. The support
3 of FIG. 2 is removed as soon as the last stack (such as 2.1) at
the upper side of this support is removed by the improved apparatus
4. The stacks 2.2 and 2.3 (and all other stacks in the layer
including the stacks 2.2, 2.3) are then ready to be depalletized in
the same way as will be described hereinafter in connection with
the removal of the selected stack 2.1.
[0039] The apparatus 4 comprises a stack displacing unit which
includes a substantially horizontal plate-like lifting implement 17
(hereinafter called plate for short) and means for moving the plate
17 in a plurality of directions (indicated by the arrows X, Y and
Z). The movements of the plate 17 include movements downwardly
toward (arrow Z) and upwardly away from the upper side of the
support 3, as well as back-and-forth movements in several (such as
two) directions (arrows X and Y) in at least substantial
parallelism with the upper side of the support 3. Such movability
of the plate 17 renders it possible to (automatically or manually)
move (arrow Z) the preferably thin (and hence relatively sharp)
leading edge 18 of the plate into actual contact with or close to
the upper side of the support 3 and to thereupon move the plate 17
in the direction of the arrow X and/or Y in order to locate the
leading edge 18 adjacent one side of the selected stack 2.1. When
such preliminary positioning of the plate 17 is completed, the
plate is ready to be moved along the upper side of the support 3 so
that its leading edge 18 is introduced between such upper side and
the underside of the lowermost blank of the selected stack 2.1 (see
FIG. 3).
[0040] The aforementioned means for moving the plate 17 in and
counter to the directions indicated by the arrows X, Y and Z
includes a carrier or head 6 which is movable up and down (arrow Z)
along upright guides 7. The upright guides 7 are movable back and
forth (arrow Y) along horizontal paths relative to a first track 8,
and the track 8 is movable horizontally (arrow X) along a further
or second track (not shown), namely along a path which is or can be
exactly normal to the horizontal paths for the upright guides 7
along the first track 8. Thus, the leading edge 18 of the plate 17
can be moved downwardly toward and upwardly away from the upper
side of the support 3 of FIGS. 2 and 3 by causing the carrier 6 to
move along the upright guides 7, and the leading edge 18 can also
be moved along the upper side of the support 3 by moving the guides
7 relative to the track 8 and/or by moving the guides 7 and the
track 8 relative to the non-illustrated second track. The means for
moving the carrier 6 relative to the guides 7, the guides 7
relative to the first track 8, and the track 8 relative to the
second track can comprise fluid-operated motors, electric motors or
any other suitable prime movers the exact design of which forms no
part of the present invention. All that counts is to provide the
displacing unit of the apparatus 4 with moving means which can
advance the plate 17 downwardly toward and upwardly away from the
upper side of the support 3 as well as along the upper side of the
support 3 so that the leading edge 18 (and thereupon an additional
(e.g., major) part of the plate) can be introduced between the
support 3 and the underside of the lowermost blank in the selected
stack 2.1.
[0041] The displacing unit of the apparatus 4 can be provided with
one or more sensors which track the movements of the plate 17
relative to the upper side of the support 3 and transmit
appropriate signals to an evaluating circuit 31 of the apparatus 4.
For example, a position sensor can be provided to generate signals
denoting the exact or approximate position of the carrier 6
relative to the upright guides 7, i.e., to indicate the level of
the leading edge 18 of the plate 17 relative to the upper side of
the support 3. Such signals can be utilized to decelerate the prime
mover for the carrier 6 when the leading edge 18 has been moved to
a level close to the desired or optimum level relative to the upper
side of the support 3.
[0042] The carrier 6 movably or fixedly supports a substantially
horizontal guide 12 for one or more reciprocable rod-like guides 13
the free end portion(s) of which carries or carry an upright guide
14 vertically movably mounting the trailing portion of the plate
17. Such trailing portion of the plate 17 is secured to a holder
16, e.g., by one or more threaded fasteners. As can be seen in
FIGS. 2 and 3, the plate 17 (which resembles or can resemble a flat
tongue with a sharp edge 18) can slope downwardly through a
relatively small acute angle in a direction from the holder 16
toward the upper side of the support 3. This renders it possible to
move the leading edge 18 into actual contact with the upper side of
the support 3 adjacent one side of the selected stack 2.1 while the
major part of the underside of the plate 18 remains spaced apart
from the upper side of such support. Reference may be had to the
aforementioned European patent No. 0 532 943 A1 which describes and
shows a plate suitable for use in the apparatus 4 of the present
invention.
[0043] The holder 16 can be said to constitute an extension of the
carrier 6 and serves to ensure a highly accurate selection of the
level of the leading edge 18 of the plate 17 relative to the upper
side of the support 3 before the plate 17 is caused to move along
the upper side of the support from the position of FIG. 2 to that
which is shown in FIG. 3. The vertical guide 14 at the free end(s)
of the vertical guide(s) 13 carries a suitable prime mover (not
specifically shown) which can move the holder 16 and the plate 17
up and down for the aforementioned purpose of selecting the exact
level of the leading edge 18 with a very high degree of
accuracy.
[0044] A sensor 9 is provided on the holder 16 to transmit (to the
evaluating circuit 31) signals denoting the exact level of the
holder 16 and plate 17 relative to the guide 14. A further sensor
11 is provided to transmit signals denoting the exact position of
the guide 14, holder 16 and plate 17 in the longitudinal direction
of the guide(s) 13, i.e., in or counter to the direction indicated
by the arrow Y. Additional sensor or sensors are or can be provided
to generate and to transmit to the evaluating circuit 31 additional
signals denoting the exact position of the plate 17 as seen in
and/or counter to the direction indicated by the arrow X and/or Y
and/or Z. All this contributes to a more accurate positioning of
the leading edge 18 relative to the upper side of the support 3
and/or relative to the selected stack 2.1. The evaluating circuit
31 is or can be designed to control or regulate the operation of
various prime movers for the carrier 6, for the first track 8, for
the second track, and for the holder 16.
[0045] The guide 12 and the guide(s) 13 can include or constitute
one or more fluid-operated (hydraulic or pneumatic) motors (e.g.,
one or more double-acting cylinder and piston units) which can move
the guide 14 toward and away from the carrier 6 in response to
actuation (by the evaluating circuit 31) of one or more valves
serving to regulate the flow of a fluid medium into and from the
cylinder chamber or chambers of such motor(s). Analogously, the
guide 14 can include or constitute a fluid-operated motor which can
move the holder 16 (or directly the plate 17) to a desired level
relative to the upper side of the support 3.
[0046] It is also possible to employ an electric motor (not shown)
in order to shift the guides 13, 14 relative to the guide 12 on the
carrier 6. Such prime mover can further enhance the accuracy of
adjustment of the position of the leading edge 18 of the plate 17
relative to the selected stack 2.1.
[0047] In order to facilitate the introduction of the leading edge
18 of the plate 17 between the upper side of the support 3 and the
underside of the lowermost blank of the selected stack 2.1, i.e., a
movement of the plate 17 from the position of FIG. 2 to the
position of FIG. 3, the carrier 6 supports at least one but
preferably two hold-down devices 19 (only one shown) which flank
the plate 17 at the leading edge 18 and can be caused to bear
against the upper side of the support 3 at least when the leading
edge 18 reaches the position of readiness for advancement beneath
the lowermost blank of the selected stack 2.1. The construction and
the mode of operation or manipulation of the carrier 6 and of the
hold-down device or devices 19 can be the same as described in the
aforementioned European patent No. 0 532 949 A1 to which reference
may be had if necessary.
[0048] A further hold-down device 21 which is supported by the
carrier 6 serves to prevent deformation of the selected stack 2.1
during lifting of such stack by the plate 17. The hold-down device
21 is movable up and down by a suitable drive 22 which is also
mounted on and thus shares the movements of the carrier 6. When the
selected stack 2.1 is enngaged from below by the upper side of the
plate 17, the upper side of the topmost blank of such stack is
engaged by the hold-down device 21 so that the configuration of the
stack 2.1 remains at least substantially unchanged during
subsequent lifting above and movement away from the support 3,
e.g., for the purpose of depositing the stack 2.1 in or on a
suitable conveyor for delivery to a packing machine or for
introduction of the stack 2.1 directly into the blank-receiving
magazine of a packing machine.
[0049] The carrier 6 further supports a blank removing device 23
having at its lower end at least one suction cup 24 or another
suitable blank attracting or lifting component which is put to use,
when necessary, to remove from the upper side of the support 3 one
or more blanks which remained on the support subsequent to removal
of all stacks or a particular stack (such as 2.1). For example, and
assuming that the leading edge 18 of the plate 17 failed to
penetrate between the upper side of the support 3 and the underside
of the lowermost blank of the selected stack 2.1 shown in FIGS. 2
and 3, the blank or blanks which remained on the support 3 upon
removal (depalletizing) of the major portion of the stack 2.1 can
be gathered and removed by the suction head 24. The upper portion
of the blank removing device 23 can include or constitute a prime
mover (e.g., a fluid-operated motor) which can change the level of
the suction cup 24 relative to the carrier 6. Such movability of
the suction cup 24 relative to the carrier 6, combined with the
movability of the carrier in and counter to the directions
indicated by the arrows X, Y and Z, suffices to ensure that the
suction cup 24 can reach and remove blanks on any given portion of
the upper side of the support 3.
[0050] In addition to its just described function of gathering
discrete blanks off the upper side of the support 3, the device 23
can perform the function of assisting or replacing the hold-down
device 21, i.e., of causing the suction cup 24 to bear upon the
upper side of the topmost blank of a stack (such as 2.1) which is
to be removed from the support 3. The arrangement can be such that,
as a rule, the suction head 24 is used as a hold-down device;
however, if one or more blanks happen to remain on a support upon
depalletizing of a complete layer of stacks, or upon removal of a
particular stack, the device 23 can be put to use as a means for
gathering and removing such stray blank or blanks. This might be
desirable for several reasons, i.e., to prevent a loose blank from
interferring with the advancement of the leading edge 18 of the
plate 17 along the upper side of a support 3 to a desired (optimum)
position and/or to ensure that a support which has been relieved of
the respective layer of stacks can be readily removed and
immediately put to renewed use in conjunction with the same pallet
or with another pallet.
[0051] In accordance with an important feature of the invention,
the apparatus 4 further comprises a unit 26 which serves as a means
for monitoring the position of the plate 17, of a selected stack
(such as 2.1) and/or of the support 3 not later than when the step
of introducing the leading edge 18 of the plate 17 between the
upper side of the support 3 and the underside of the selected stack
is completed. The monitoring unit 26 comprises means 29 for
generating signals which denote the monitored position of the plate
17, selected stack and/or support 3 and for transmitting such
signals to the evaluating circuit 31. The purpose of the monitoring
unit 26 and of its signal generating means 29 is to generate defect
signals when the actual introduction of the plate 17 between the
upper side of the support 3 and the underside of a selected stack
(2.1) departs from a desirable or optimum introduction.
[0052] For example, and as shown in FIG. 3, the just completed
introduction of the leading edge 18 of the plate 17 beneath the
stack 2.1 was unsatisfactory because the leading edge 18 has been
caused to penetrate through the adjacent portion of the support 3
and the latter actually overlies such leading edge. In other words,
the leading edge 18 is located at the underside, in lieu of at the
upper side, of the support 3.
[0053] The monitoring unit 26 is designed to monitor the position
of that portion of the support 3 which is adjacent the plate 17
when the aforediscussed introducing step is completed. To this end,
the unit 26 comprises an optical position sensor including a source
of radiation 32 (such as light). The source includes or is adjacent
the upper end of a light conductor 28 having a radiation
discharging/receiving end 27 serving to direct at least one beam of
radiation 32 toward the upper side of (e.g., through a window in)
the plate 17. The radiation which is reflected back into the
conductor 28 is transmitted to the signal generating means 29 which
generates a defect signal (under the circumstances prevailing in
FIG. 3) or a signal denoting that the plate-introducing step has
been completed in a satisfactory manner, i.e., that the partially
lifted selected stack can be moved off and away from the upper side
of the support 3 to be delivered to a conveyor or into a magazine
for blanks.
[0054] The actual radiation source can be installed in or can form
part of the signal generating means 29. Thus, a beam of radiation
32 can issue from the source of the signal generating means 29 to
be propagated in the conductor 28, to issue at the end 27, to be
reflected by the support 3 back into the end 27, and to be
propagated in the conductor 28 back to the signal generating means
29 which generates a signal denoting the position (level) of that
portion of the support 3 which is adjacent the plate 17. The manner
in which a signal generating means (29) can emit radiation and can
be provided with a suitable transducer for the generation and
transmission (to the evaluating circuit 31) of signals which are
indicative of the monitoring of the position of the support 3 at
the plate 17 is well known to those skilled in the relevant
arts.
[0055] As already mentioned above, the evaluating circuit 31
receives and processes several additional signals including those
transmitted by the sensors 9 and 11 (as well as by one or more
additional sensors, if any). The evaluating circuit 31 is shown as
a discrete component part of the apparatus 4; however, it is often
preferred to integrate the evaluating circuit 31 into the control
circuitry of the machine or production line in which or in
conjunction with which the apparatus 4 is being put to use.
[0056] The operation of the apparatus 4 is as follows:
[0057] It is assumed that the apparatus is to lift the selected
stack 2.1 of FIG. 2 off the upper side of the support 3. The first
step involves the positioning of the carrier 6 relative to the
upright guides (arrow Z), the guides 7 relative to the first track
8 (arrow Y) and the first track 8 relative to the second track
(arrow X), as well as the holder 16 (by way of the parts 12, 13,
14) relative to the carrier 6 and holder 14, in such a way that the
leading edge 18 of the plate 17 assumes a desired position relative
to the selected stack 2.1 Thus, and as shown in FIG. 2, the leading
edge 18 is closely adjacent the upper side of the support 3 at a
locus closely or immediately adjacent the nearest edge of the
lowermost blank of the stack 2.1. The hold-down devices 19 are
operative, i.e., they are caused to depress the adjacent portions
of the support 3 so that the leading edge 18 is even more likely to
penetrate between the upper side of the support 3 and the underside
of the lowermost blank forming part of the selected stack 2.1.
[0058] Alternatively, the leading edge 18 of the plate 17 can be
moved to the position of FIG. 2 in two successive stages. The first
stage can involve a coarse adjustment by the carrier 6 (arrows X,
Y, Z) and holder 16 (via guides 12, 13, 14) so that the leading
edge 18 is moved to a position reasonably close to the desired or
optimum position for penetration between the support 3 and the
stack 2.1. The next-following second stage involves a precision or
final adjustment of the position of the leading edge 18, e.g., with
assistance from one or more sensors (not shown) at or close to the
hold-down devices 19. Such sensor or sensors can generate signals
which are evaluated by the circuit 31 and are utilized to effect
final adjustments of the leading edge 18 (i.e., of the plate 17) in
the directions of the arrows X and Y. Moreover, a signal from the
sensor 9 can be utilized to thereupon move the holder 16 and the
plate 17 relative to the guide 14 (arrow Z) so that the leading
edge 18 is immediately adjacent or actually contacts the upper side
of the support 3 at the hold-down devices 19.
[0059] The movement of the holder 16 and plate 17 relative to the
guide 14 is terminated when the signal from the sensor 9 to the
evaluating circuit 31 indicates that the leading edge 18 is located
at an optimum level relative to the upper side of the support 3.
That position of the leading edge 18 which is shown in FIG. 2 is
presumed to be an optimum position, i.e., a position which is least
likely to cause any problems in the course of the next-following
steps which normally involve the introduction of an adequate
portion of the plate 17 between the support 3 and the stack 2.1,
lifting of the plate 17 and of the stack 2.1 above and away from
the support 3, and the transfer of the stack 2.1 from the plate 17
onto a conveyor, into a magazine or to another destination.
[0060] The movement of the plate 17 from the position of FIG. 2 to
the position of FIG. 3 is effected by moving the guides 13 and 14
(with the holder 16) relative to the guide 12 and/or by moving the
upright guides 7 along the first track 8. Thus, the movement of the
plate 17 from the position of FIG. 2 to the position of FIG. 3
takes place along a horizontal path defined by the guide(s) 13. If
the leading edge 18 encounters an obstruction, such as an upwardly
projecting portion of the support 3, the plate 17 penetrates into
and through the relatively thin support in a manner as shown in
FIG. 3 so that the leading edge 18 is located beneath (rather than
at a level above) the adjacent portion of the support. For example,
a portion of the support 3 beneath the selected stack 2.1 (above
the stack 2.3) can be caused to bulge upwardly as a result of the
action of the hold-down devices 19 in combination with frictional
engagement between the leading edge 18 and the upper side of the
support 3. The leading edge 18 is caused to cut an elongated slot
in the support 3 on its way to the position which is shown in FIG.
3.
[0061] If the undesirable penetration of the plate 17 through the
support 3 is not detected in time, i.e., if the plate 17 is
thereupon caused to move upwardly in order to advance the stack 2.1
above and away from the stack 2.3, the plate 17 lifts and
ultimately tears up that portion of the support which overlies the
plate. If the stack 2.1 is not the last stack of the layer of, for
example, thirtyfive stacks (see FIG. 1) on the support 3 of FIG. 3,
at least some of the stacks adjacent the stack 2.1 are overturned,
partially overturned or otherwise affected so that they are no
longer in conditions for predictable depalletizing. Each such
occurrence necessitates a lengthy interruption of the depalletizing
operation in order to enable one or more attendants to remove all
affected stacks before the plate 17 can be caused to resume the
removal of remaining stacks off the pierced support 3 or off the
next-following (lower) support.
[0062] In order to ensure timely detection of a less than
satisfactory operation of the apparatus 4, each depalletizing
operation preferably includes the additional step which is shown in
FIG. 3. Thus, prior to actually removing a stack (2.1) which at
least partially overlies the plate 17, the latter is moved upwardly
through a predetermined distance (e.g., in the range of one or more
millimeters, preferably about 10 mm) to lift the stack 2.1 and to
enable the monitoring unit 26 to even more reliably and accurately
ascertain whether or not the monitored part of the support 3 at the
plate 17 is in a position which is indicative of satisfactory
lifting of the stack 2.1 above and away from the support. The plate
17 can be lifted by the carrier 6 which is caused to move upwardly
(counter to the direction indicated by the arrow Z) along the
upright guides 7 and thus lifts the plate 17 by way of the guides
12, 13, 14 and holder 16.
[0063] The monitoring unit 26 is caused to ascertain the position
(and hence the condition) of the support 3 at the plate 17 as soon
as the upward movement of the plate 17 through the distance of a
few millimeters is completed. The beam of radiation 32 issuing from
the signal generating means 29 passes through the plate 17 (e.g.,
via the aforementioned window in the plate) and is reflected by the
raised portion of the support 3 beneath the plate 17. The thus
reflected radiation causes the signal generating means 29 to
generate a defect signal which is displayed or is rendered audible
or is otherwise processed, e.g., by the evaluating circuit 31. A
signal which is generated at 29 when the leading edge 18 did not
penetrate through the support 3 in a manner as shown in FIG. 3 is
sufficiently different from a defect signal to permit unimpeded
continuation of the depalletizing operation.
[0064] The arrangement is preferably such that, if the signal
generating means 29 transmits to the evaluating circuit 31 a defect
signal, the circuit 31 prevents any further movements of the plate
17 and of the stack (2.1) thereon until the cause of malfunction
(irregularity in the depalletizing operation) is detected and
eliminated. In fact, a defect signal which is furnished by the
signal generating means 29 and is processed by the evaluating
circuit 31 can be utilized to effect a temporary stoppage of the
machine or production line which receives stacks of blanks from the
plate 17.
[0065] FIG. 3 illustrates only one of defective operations which
can be detected by the monitoring unit 26 or an equivalent
monitoring unit. Penetration of the leading edge 18 of the plate 17
into a support 3 of cardboard or the like has been illustrated in
FIG. 3 because it is one of more frequent causes of malfunctioning
of the depalletizing apparatus 4. The aforedescribed lifting of the
plate 17 through a short distance prior to actual evacuation of the
stack overlying the plate 17 constitutes an optional but highly
desirable feature because it contributes to the reliability of
detection of defective operation of the apparatus 4 and/or of flaws
in a support 3 and/or of excessive resistance of the lowermost
blank of a stack to separation from the upper side of the support
below it so that the plate 17 is compelled to damage or further
damage or displace the support during advancement of the leading
edge 18 from the position of FIG. 2 to that shown in FIG. 3.
[0066] The improved apparatus is susceptible of numerous additional
modifications. For example, at least the conductor 28 of the
optical detector forming part of the monitoring unit 26 can be
mounted on one of the hold-down devices 19 or on the plate 17 or on
the carrier 6. In fact, the signal generating means 29 can be
mounted on one of the hold-down devices 19 or on the plate 17 or on
the carrier 6 so that the conductor 28 can be dispensed with.
[0067] Furthermore, an optical monitoring unit 26 can be utilized
in combination with or it can be replaced by a suitable mechanical
or fluid-operated (pneumatic or hydraulic) monitoring unit. All
that counts is to provide the apparatus 4 with a suitable
monitoring unit capable of generating defect signals when a
depalletizing operation is not being carried out in a prescribed or
acceptable manner, e.g., when the leading edge 18 of the plate
(implement) 17 has penetrated into the adjacent portion of a
support.
[0068] The generation of a defect signal can be utilized to alert
one or more attendants or to initiate an automatic remedial action,
e.g., the transfer of one or more stacks into a collecting
receptacle for waste material before the normal depalletizing
operation is resumed.
[0069] In lieu of or in addition to monitoring of the support 3,
the apparatus 4 can be equipped with means for monitoring the
dimensions, the shape, the weight and/or other parameters or
characteristics of successive stacks in order to ascertain whether
or not the stacks are ready to be transported into a packing or
other blank processing machine.
[0070] As concerns the various types of monitoring units which can
be utilized in the apparatus of the present invention, reference
may be had to any one of numerous available publications dealing
with pneumatic, hydraulic, mechanical, optical and other sensors.
For example, the part of the article by S. L. Sorsen on pages 77
and 79 in the May 1964 issue of the publication entitled "Control
Engineering" describes and illustrates various modes of monitoring
the quality, speed, position and height difference of sheets made
of paper, steel, plastics and/or textile materials. The
illustrations show the basic components (limit switches) of
mechanical monitoring means, of light- or air-operated presence
detectors, as well as of various proportional sensors. It is
believed that a pneumatic proximity proportional sensor of the type
shown and described at 10 on page 79 of the article by Sorsen is
particularly suitable for use with or in lieu of the monitoring
unit 26 shown in FIGS. 2-3. Such monitoring units, as well as
numerous updated versions thereof, can be utilized with or as
substitutes for the monitoring unit 26 of FIGS. 2-3 without
departing from the spirit of the invention.
[0071] An advantage of the apparatus 4 which is shown in FIGS. 2
and 3 is that a defective depalletizing operation can be detected
(and the necessary remedial steps undertaken) before a defective
stack or a defect in the support affects the condition of other
stacks on the same support.
[0072] Another important advantage of the improved method and
apparatus is that a defective depalletizing operation can be
detected immediately after occurrence so that a remedial action can
be undertaken before the start of a chain reaction, i.e., of a
series of two or more unsatisfactory depalletizing operations. This
shortens the intervals of idleness of the blank processing machine
and reduces the numbers of blanks or stacks of blanks which are
damaged or otherwise affected as a result of a defective
depalletizing operation. Thus, even a rather serious malfunction,
such as that shown in FIG. 3, does not or need not cause
substantial losses in output and/or damage to a large number of
blanks.
[0073] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic and
specific aspects of the above outlined contribution to the art of
depalletizing commodities and, therefore, such adaptations should
and are intended to be comprehended within the meaning and range of
equivalence of the appended claims.
* * * * *