Note: Descriptions are shown in the official language in which they were submitted.
' i
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Bartholomy 5~'i~
Bartholomy & Co. s
VACUUM LIFTER
Description
The invention concerns a vacuum lifter for moving loads with adhesion surfaces
and comprising at least one suction head with several annular seals projecting
from its
suction side while forming vacuum spaces enclosed by said seals, said vacuum
spaces commu-
nicating with a vacuum source which communicates with the outer vacuum spaces)
by
valves) controlled by sensors measuring the magnitude of the load's adhesion
surface.
As a rule such vacuum lifters are used as crane accessories, however they are
,o also mounted on conveyance means such as fork lifts with lift masts, on
balancing equipment,
manipulators, roller reversers or the like. Multiple mountings also are
possible. Such
vacuum lifters for instance allow raising and conveying rolls of wound bands
for instance
made of paper, metal, plastic or laminates, and, depending on the shape of the
suction head,
by coming to rest against the end face or the periphery of the prone or
upright roll. Flat
,s bodies also, for instance panels, may be transferred by such vacuum
lifters.
A vacuum lifter of this species illustratively is described in the German
Gebrauchsmuster 84 35 161.6. Its suction head is a plane suction plate to the
lower side of
which are mounted several concentrically spaced annular seals. These annular
seals enclose
mutually separated vacuum spaces which, when the suction plate is deposited on
the
Zo pertinent adhesion surface of a load to be transported, will form sealed
annular chambers
when and if the load is covered. The "annular" seals need not be circular but
may be of any
other shape, for instance being oval or polygonal provided they form a closed
ring. Nor is
it necessary that they be one inside another. They rnay also enclose adjacent
vacuum spaces
or be distributed over several suction plates.
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8artholomy 5824
The vacuum spaces are connected through apertures in the suction plate with
a vacuum source, for instance a pump. A valve is associated with each of at
least the
vacuum chambers outside the inner one and is present in the connection to the
vacuum
source. Each valve is coupled to a sensor measuring the magnitude of the
adhesion surface
s of the load when the vacuum lifter is lowered. The sensor is always mounted
in such a way
that it opens the valve when the load adhesion surface is so big that the
associated vacuum
chamber shall be completely sealed upon deposition on the adhesion surface. In
this manner
only those vacuum spaces that form closed annular chambers after deposition of
the vacuum
lifter on the load shall reliable communicate with the vacuum source and
therefore shall not
,o suck-in unwanted air.
In particular mechanical pickups are applicable as sensors to control the
valves,
and these sensors project downward over the plane of the annular seals and
will be forced
upward by the load adhesion surface when suction is applied. However other
sensors, for
instance optical ones, also are conceivable. The mechanical pickups always are
mounted on
,s the outside of the pertinent annular seal because thereby the associated
valve shall reliably
be opened only when the load adhesion surface is larger than the associated
annular or
vacuum chamber.
Now it may happen that the diameter of the load adhesion surface is precisely
the same size as the outside diameter of one of the annular seal, so that the
adhesion
zo surface does not project outward beyond the annular seal. Consequently the
associated
sensor mounted on the outside of this annular seal will not measure, and in
the event of
being a measuring pin, will not be forced upward. In that event the associated
valve shall
not be opened, whereby, in turn, the vacuum space enclosed by this annular
seal remains
unconnected to the vacuum source and therefore is not evacuated. Provided the
vacuum
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eennobmy se2v
spaces inward from this vacuum space generate enough holding force to move the
load, no
drawback regarding moving the load is incurred for the time being.
However problems do arise when thereafter raising the vacuum lifter off the
deposited load. In this procedure the annular seals that were elastically
compressed by
s means of the vacuum during the transport elastically move apart, so that
during a short
segment of the raising motion they remain in contact with the load adhesion
surface. The
inner, vented vacuum spaces can then draw in air, but not the outer vacuum
space that was
not, subjected to vacuum during said transport. Because of the elastic outward
motion of the
annular seals, an undesired vacuum suction force has been created. If it is
less than the
,o weight of the load that was just deposited, then as the vacuum lifter is
raised off, detachment
takes place impulsively with possible errors in control sequence. If the
vacuum farce were
to be larger than the weight of the deposited load, then initially this load
is carried along.
The air which no longer is evacuated and now follows the load is the
predominant cause of
the collapse of the vacuum suction in this vacuum chamber, whereby the load
crashes in
~s uncontrollable manner and is damaged. Moreover there is significant danger
of an accident,
US patent 3,999,795 describes a vacuum lifter of which the vacuum head
comprises three suction plates each with one annular seal. These three suction
plates are
not associated each with one valve, instead only with one central valve by
means of which
communication with the vacuum source may be set up. Moreover compressed air
equipment
zo is provided, which includes an injector feeding a de-icing liquid. By
switching the central
valve, de-icing liquid can be periodically supplied to the vacuum chambers,
the compressed
air ensuring atomization.
Moreover a vacuum lifter is disclosed in US patent 3,865,420 which comprises
a vacuum head with a plurality of suction cups whereby for instance eggs can
be moved. The
H
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Barthotomy 5824
vacuum head communicates with a vacuum pump acting as the vacuum source, and
the
vacuum head aIternatingly can be connected to the suction or the pressure side
of the
vacuum pump. However such a design is unsuitable for vacuum lifters of the
above species.
The object of the invention is to so design a vacuum lifter of the initially
cited
s kind that impulsive detachment and especially unwanted, renewed lifting of
the load follow-
ing its deposition shall be avoided under all conditio»s.
This problem is solved by the invention in that a compressed-air system is
associated with at least one of the vacuum chambers and in that a control
system is provided
which, following detection that the communication with the vacuum source was
interrupted
,o and following venting of this (these) vacuum chamber(s), shall turn ON the
compressed-air
system for a given time, a blocking valve to interrupt venting also being
present. The
blocking valve preferably is in the form of a check-valve.
The compressed air system being controlled in this manner, it is possible to
produce excess pressure whereby the vacuum lifter is reliably separated from
the deposited
,s load and thus overcomes the suction formed in the vacuum chamber which, far
the reasons
described above, is out of communication during transport with the vacuum
source. Prefera-
bly the compressed air system is connected only to the inner vacuum chamber
because
therein sufficient excess pressure can be produced in any event.
In a further development of the invention, a pressure sensor measuring the
zo pressure in the associated vacuum chamber is part of the automated control
system and so
affects said automated control system that the compressed air system shall be
turned ON
only after the pressure has risen in the associated vacuum chamber above a
given value,
preferably near atmospheric pressure. Instead of the pressure sensor, a timing
link also may
be provided that appropriately affects the automated control system.
*. CA 02052241 2003-O1-03
74930-4
4a
In accordance with the present invention, there is
provided a vacuum lifter (1) for the transport of loads (3)
having an adherent surface, with at least one suction head
(5) having suction face which has a plurality of protruding
ring seals (10, 11, 12) thereon forming vacuum spaces (13,
14) enclosed by the said ring seals and which are connected
to a vacuum generator (16, 60), wherein the vacuum generator
is connected to at least one of said outer vacuum spaces via
valves (34) which are controlled via sensors (43) each of
which scans the size of the adherent surface, characterised
in that a compressed air device (51, 52, 53) is associated
with at least one of the vacuum spaces (13) and a controller
is provided which connects the compressed air device (51,
52, 53) for a certain time after detecting an interruption
of a connection to the vacuum generator (16) and after
aeration of the said vacuum space (13), wherein a stop valve
(22) is provided for interrupting said aeration.
~~~~~~i
g~,~b~, ~. 5
Appropriately the compressed air system includes a compressed-air reservoir
to ensure adequate available compressed air at all times.
The invention is illustrated in the drawing by means of a schematic, vertical
section of an embodiment. The right-hand part of the invention has been
omitted from the
drawing which shows the left and center parts of a vacuum lifter 1 seated on
the top side 2
of an upended paper roll 3 comprising an inside winding tube 4. The paper web
is wound
on this winding tube 4.
The main part of the vacuum lifter 1 is a vacuum vessel 5 which is circular in
topview. It is made in welded, vacuum-tight manner and its lower seal is a
suction plate 6
,o while at the top it has a top plate 7. A center pipe 8 is present at the
center zone and forms
the internal seal of the vacuum vessel 5. On the outside the vacuum vessel 5
is sealed by a
peripheral side wall 9.
Three elastomeric annular seals 10, 11, I2 are mounted concentrically with the
center vertical axis of the vacuum lifter 1 at the lower side of the suction
plate 6. By means
,s of these annular seals 10, 11, 12 the vacuum lifter 1 rests on the top side
2 of the paper roll
3. The inner annular seal 10 is of such a large diameter that it falls outside
the winding tube
4, as a result of which no unwanted air can be aspirated through the winding
tube 4.
Together with the farther out center annular seal 11, the inner annular seal
10 forms an
inner, annular vacuum space 13. The outer annular seal 12 together with the
center annular
seal 11 forms another, annular and outer vacuum space 14 separated by the
center annular
seal 11 from the inner vacuum space 13. If the vacuum lifter 1 has a larger
diameter, further
vacuum spaces toward the exterior may be provided in corresponding manner.
The vacuum vessel 5 communicates through a vacuum line 15 with a vacuum
source 16. The vacuum source 16 is connected to an angular-speed control 17
and moreover
Beltholomy 5824
comps ises a check valve 18. The vacuum source 16 keeps the vacuum vessel S
acting as a
reservoir to a constant, specific reduced pressure.
A vacuum pipe 19 issues from the vacuum vessel S and leads to a three-way
valve 20 which is driven electromagnetically. The three-way valve 20 comprises
an outlet 21
equipped with a check valve 22 to set up communication to atmospheric air.
Moreover a
pipe 23 is connected which comprises a control valve 24 and which receives a
through-pipe
2S. The through-pipe 2S passes through the vacuum vessel S and is open toward
the inner
vacuum space 13.
The control valve is connected through a control line 26 to a test-value trans-
,o ducer 27 cooperating with a test-value pickup 28 which in turn is connected
through a test
line 29 passing through the vacuum vessel S to the inner vacuum space 13.
Another control
line 30 shown in dashed lines is connected to the angular-speed control 17.
In the shown position of the three-way valve 20, the vacuum vessel 5 communi-
cafes through the vacuum pipe 19, the three-way valve 20, the pipe 23, the
control valve 24
,9 and the through-pipe 2S with the inner vacuum space 13. Said space
therefore is subjected
to full vacuum, which is set by means of the control valve 24 at a specific
value detected by
means of the test line 29, the test-value pickup 28 and the test-value
transducer 27 and fed
as a control value to the control valve 24. Further control of the vacuum
takes place by
means of the angular-speed control 17.
If the vacuum of the inner vacuum space 13 shall be eliminated, then the three-
way valve 20 is switched. In this manner the pipe 23, the through-pipe 2S and
hence the
inner vacuum chamber 13 communicate through the check valve 22 with the
atmosphere, that
is, the inner vacuum space 13 is vented. Simultaneously the previously extant
communication
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a~,~b~, ~.
between the vacuum line 15 and the pipe 23 is interrupted, that is, the vacuum
in the vacuum
vessel 5 is maintained.
A vacuum box 31 is seated on the external part of the top plate 7 of the
vacuum vessel 5. The inner space 32 of this box 31 communicates by means of a
through-
s pipe 33 passing through the vacuum vessel 5 with the inner vacuum space 13,
that is, the
inner space 32 is at the same pressure as is present in the inner vacuum space
13.
At its bottom side the vacuum box 31 comprises a valve part 34 cooperating
with a valve head 35. The valve head 35 is mounted on a hollow valve rod 36
open at its
top and bottom sides. By its upper end the valve rod 36 rests inside a valve-
rod guide 37.
,o A further valve-rod guide not shown herein in further detail is present
near the lower end
of the valve rod 36. A compressing helical spring 3$ encloses the valve rod 36
in the zone
of the inside space 32 and rests at its top against the valve-rod guide 37 and
at its bottom
against a collar 39 above the valve head 35. Accordingly the valve head 35 is
spring-loaded
toward the valve port 34.
,s The valve port 34 continues downward into a filter pipe 40 passing through
the
vacuum vessel 5 and issuing into the external vacuum space I4. A filter insert
41 is mounted
inside the filter pipe 40 and allows the suction air from the external vacuum
space 14 to flow
through it when the valve head 35 is raised off the valve port 34.
A guide pipe 42 is mounted externally on the side wall 9 of the vacuum vessel
?o S and inside of it a mechanical detecting pin 43 is held relatively loosely
so as to be vertically
displaceable. It is located immediately next to the outside of the external
annular seal 12.
An actuation rod 44 is supported in vacuum tight manner above and in the
axial extension of the mechanical detecting pin 43 in the lower and upper
walls of the
vacuum box 31. Said pin is enclosed in the zone of the inside space 32 of the
vacuum box
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8artholomy 5824
31 by a compressing helical spring 45 generating the same spring force as the
helical spring
38 of the valve rod 36. The helical spring 45 rests agaimt the tog wall of the
vacuum box
31 and at the bottom against a forked lever 46 rigidly affixed to the
actuation rod 44. The
forked lever 46 extends horizontally as far as the valve rod 36 where it
enters in geometrical-
s 1y locking manner between the collar 39 and the valve head 35. In this
manner the valve
head 35 follows the motions of the actuation rod 44.
The actuation rod 44 projects upward out of the vacuum box 31 into a compen-
sating cylinder 47 where it comprises at its end a compensating piston 48
moving in sealed
manner inside the compensating cylinder 47, the piston surface corresponding
to that of the
,o valve head 35. The space above the compensating piston 48 is connected
through a compen-
sation line 49 to the valve-rod guide 37. The space underneath the
compensating piston 48
communicates through a compensating borehole 50 with the inside 32 of the
vacuum box 31.
As regards large vacuum lifters with additional external vacuum spaces, each
vacuum space is arranged in a prescribed manner, the particular vacuum boxes
communicat-
,s ing with the particular nearest inner vacuum spaces.
In the embodiment shown, the detection pin 43 is in its lowest position
because
the diameter of the paper roll 3 just coincides with the outside diameter of
the outer annular
seal 12. When the vacuum lifter 1 is deposited on the paper roll 3, the valve
head 35
therefore will not be raised. Thereby the vacuum forces acting on the valve
head 35 in the
zo direction of opening because of the vacuum in the inside space 32 and those
acting through
the compensation borehole 50 on the lower side of the compensation piston 48
will balance
on account of the essentially coinciding diameters of the valve head 3S and
compensation
head 48, that is, the actuation rod 44 and thereby the forked lever 46 is
forced down by a
force corresponding to that acting on the valve head 35 in the direction of
opening. Because
2Q52241
Barltwlomy 5824
of this balance the valve head 35 is pressed merely by the helical springs 38,
45 against the
valve port 34.
In the typical case the diameter of the paper roll 3 does not precisely match
-- and this is shown in the Figure -- the outside diameter of the external
annular seal 12.
If the diameter is larger, then the detecting pin 43 is not yet actuated when
the vacuum
lifter 1 has been deposited because projecting less than the annular seals 10,
11, 12 even
when these are somewhat compressed by the weight proper of the vacuum lifter
1. It is only
when the three-way valve 20 has been moved into the shown position, whereby
the vacuum
space 13 is subjected to full vacuum, that the annular seals 10, 11, 12 will
be compressed
,o so strongly that the detection pin 43 comes to rest against the top side of
the paper roll and
even is forced upward. Thereby it also bridges the distance between its upper
end and the
lower end of the actuation rod 42 which it carries along.
Thereupon, by means of the forked lever 46, the valve head 35 is raised off
the
valve port 34 against the action of the helical springs 38, 45. In this manner
the outer
vacuum chamber 14 is also evacuated through the filter pipe 40, the valve port
34, the
vacuum box 31 and the through-pipe 33. By raising the valve head 35, pressure
balancing
takes place at its top and bottom sides, whereby, in the absence of further
steps, the force
generated by the vacuum at the lower side of the compensation piston 48 would
move the
actuation rod 44 and hence the valve rod 36 down again. However, the valve rod
36 being
Zo hollow and there being communication through the compensation line 49 to
the compensa-
tion cylinder 47, the space above the compensation piston 48 also is
evacuated, whereby the
initially extant pressure differential is eliminated.
After the paper roll 3 has been deposited, and as already described above, the
inner vacuum space 13 is vented by actuating the three-way valve 20. This
venting also
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Barthobmy 5824 10
affects the inside space 32 of the vacuum box 31 and thereby the outer vacuum
space 14
because the valve head 35 is still open. When the vacuum lifter 1 is being
raised, the
detection pin 43 again moves out of its guide tube 42 and as a result the
valve head 35 and
the actuation rod 44 descend again on account of the action of the helical
springs 3~ or 45
until the valve head 35 has sealed the valve port 34.
The above-described situation assumes that the paper roll 3 is of a diameter
larger than shown, whereby the detection pin 43 shall be raised when the
lifter comes down.
However that is not the case in the present embodiment mode, and therefore the
detection
pin 43 remains in its downwardly projection position. As a result, the valve
port 34 remains
,a sealed even though the outer vacuum space 14 is closed by the top side 2 of
the paper roll
3 and could be evacuated. The surface of the inner vacuum space 13 however is
chosen in
such a way that, in these instances, the suction said space does exert
suffices to lift the paper
roll 3 and to transport it while it is suspended, and there is no need for
vacuum in the outer
vacuum space 14 in such cases. However when depositing the load and then
raising the
,s vacuum lifter 1, the problem arises that here a vacuum is generated by the
elastic motion of
the annular seals 11, 12 in the outer vacuum space 14 -- because, contrary to
the case of the
vented inner vacuum space 13, no air can follow. This may result in the paper
roll 3 raised
by the vacuum lifter 1 being moved over some distance until the vacuum formed
in the outer
vacuum space is slowly eliminated by air entering through the material of the
paper roll 3
zo until the paper roll 3 no longer is supported. Thereupon it crashes in
uncontrolled manner.
In a preventive step, a compressed-air source 51 is provided which communi-
Gates through a compressed-air line 52 with a compressed-air reservoir 53 and
through a
magnetic valve 54 with the inside space 32 of the vacuum box 31. Ordinarily.
the magnetic
valve 54 is closed. After the paper roll 3 has been deposited and the three-
way valve has
w 2052~4i
Bartholomy 582~ 11
been switched to the venting position, the magnetic valve 54 is opened by an
automatic
control not shown in further detail herein once the pressure in the vacuum
space 13 has risen
to nearly atmospheric. Thereby the inside space 32 of the vacuum box 31 is
raised to excess
pressure and also, by means of the through-pipe 33, the inner vacuum space 13.
The check
valve 22 prevents the air from flowing out through the pipe 23 and through the
three-way
valve 20 in the venting position. The excess pressure building up in the inner
vacuum space
13 suffices to raise the vacuum lifter 1 off the paper roll 3 and to overcome
the vacuum force
forming in the outer vacuum space 14 on account of the elastic motion of the
annular seals
11, 12. The paper roll 3 no longer is carried away when it is not supposed to
be. The supply
,o of compressed air is shut down at once after the vacuum lifter 1 has been
raised, and this
process is automatically controlled by corresponding pressure sensors.
The vacuum lifter 1 is centrally suspended from a crane travel works not shown
herein in further detail. Its lower flange is connected with a support bolt 55
displaceably
resting on slide blocks 56 in a vertical guide 57. The support bolt 55 widens
at its lower side
,s and thereby rests upwards against a cup spring 58. A limit switch 59 is
mounted in the lower
part of the vertical guide 57 and will be actuated once the slide blocks 56
have reached their
lower end position. The limit switch 59 is coupled by a control means not
shown in further
detail herein with the three-way valve 20.
When the paper roll 3 is deposited, the crane travel works becomes slack
whereby the
?o slide blocks 56 together with the support bolt 55 will descend. By
actuating the limit switch
59, the three-way valve 20 is switched from the shown position, wherein vacuum
exists in the
inner vacuum space I3, to the venting position, so that the inner vacuum space
13 automati-
cally is connected to the atmosphere. Another limit switch not shown in
further detail here
is connected as a slack-cable safety device to the crane travel works and
turns it off
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Bartholony 5824 12
automatically. Additionally the limit switch 59 may also be connected to the
magnetic valve
54 of the compressed-air source S1, whereby the inner vacuum chamber 13 is not
only vented
but also simultaneously fed with compressed air, Thereupon the vacuum lifter 1
can be
raised off the paper roll 3.
When the slide blocks 56 move away from the limit switch 59, a control system
ensures that the three-way valve 20 shall not be switched, rather that this
switching shall take
place only after the vacuum lifter 1 is lowered again on a new paper roll , in
the process of
which the slide blocks 56 are lowered onto the limit switch 59. However a
different logic
circuit may also be provided, or the resetting of the three-way valve into the
vacuum position
,o may be carried out by the operator.
Additionally the vacuum lifter 1 comprises an emergencyw vacuum source 60
communicating through an emergency vacuum line 61 with the inner space of the
vacuum
vessel 5. The emergency vacuum source 60 also is secured by a check valve 62.
The
emergency source 60 is driven by a DC motor 63 connected by a pressure switch
64 to a
,s battery 65. The battery 65 is connected to a battery-charging apparatus 66
permanently
connected to the power supply and in this manner is continuously kept
optimally charged.
The pressure switch 64 is connected to a test-value pickup 67 in turn
connected
through a test line 68 with the inside of the vacuum vessel 5. The test-value
transducer 67
is set in such a way that it emits a closet signal to the pressure switch 64,
which is a magnetic
so switch, when the test line 68 ascertains that the vacuum in the vacuum
vessel 5 has dropped
below a specified minimum value. Thereby the DC motor 63 will be actuated, and
hence
the emergency vacuum source 60, and the vacuum drop in the vacuum vessel 5
will be
compensated and the normal vacuum level shall be reached again. At the same
time, a
I
Bartholomy 3824 13
signal generator 69 emits a malfunction signal to reliably alert the operator
that the vacuum
produced by the vacuum source 16 is inadequate to move the paper roll 3.
A remote control line 70 also starts from the pressure switch 64 to allow an
operator to actuate the pressure switch 64 also independently from or
alternatively to the
s above described automated system in order to start the emergency vacuum
source 60.
Illustratively a drop in vacuum may be caused by a malfunction of the vacuum
source 16, but also because the vacuum-grip properties of a paper roll 3 have
degraded the
time-dependent visco-elastic and hygroscopic behavior to such an extent that
the vacuum
source 1b no longer suffices for sufficient vacuum. In that case the emergency
vacuum
,o source 60 may additionally be used as required by the operator.
Furthermore, the term vacuum is to be construed as a pressure less than
atmospheric.
