Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACXGROUND OF THE INVENTION
This invention relates to an apparatus ~or spreading
open flat bags which are open along one edge~ The apparatus
includes an air-pervious suction belt trained about two end
rollers, at least one of which is driven. The suction belt
lo has a flight having one face oriented towards the bags to be
conveyed and another, reverse face which is exposed to
vacuum.
An apparatus of the above-outlined known type is dis-
closed in United States Patent No. 3,631,768. The apparatus
first folds a ~heet to form an upwardly open hose. Sealing
shoes and severing knives ~orm upwardly open, individual bags
~ro~ the hos~ an~ ~he bags are separated from one another as
they pass through the suction belt. Thereafter, the bags are
grasped by grippers at their longitudinal edges, and the two
grippers which grasp ~ bag are moved towards one another
whereby the bag spreads open. Subsequently, the bag is
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charged with good~ and sealed. Such an apparatus needs
substantial space and reliably spreads the bag open only when
the bag material is relatively stiff.
SUMMARY OF THE INVENTION
It is an ob~ect of the invention to provide an improved
apparatus of the above-outlined type which reliably spreads
open the bags even if the bag material is soft and further,
the apparatus is of significantly shorter construction than
prior art assemblies.
This object and others to become apparent as the
specification progresses, are accomplished by ~he invention,
according to which, briefly stated, the apparatus for
spreading open flattened bags has a first air-pervious
endless belt having a working flight provided with a workiny
face and an ~pposite, reverse face; and a second air-pervious
endless bel~ having a working flight provided with a working
~ace and an opposite, reverse face. The working flights of
the first and second belts are divergent at an acute angle in
the bag conveying direction. There i~ :Eurther provided a
suction device genera~ing a vacuum for urging a gas to flow
across ~he working flights in a direction from the working
face to the reverse face of each working flight, whereby each
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bag introduced between the working flights adheres, with
opposite bag panels, to the working faces of the working
flights and i6 forwarded thereby in the conveying direction,
while being gradually spread open.
RIEF DESCRIPTION OF THE DRAWING
Figure 1 is a schematic side elevational view of a
preferred embodiment of the invention.
Figure 2 is a schematic top plan view of the preferred
embodiment.
Figure 3 is an enlarged sectional view taken along line
III-III of Figure 2.
Figure 4 is an enlarged sectional view taken along line
IV-IV of ~igure 2.
Figure 5 i~ an enlarged sectional view taken along line
V-V o~ Figure 2.
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DESCRIPTION OF THE PREPERRED EM30DI~NT
Turning to Figures 1 and 2, the apparatus illustrated
therein serves for conveying, separating and spreading open
upwardly open flat bags 1. A web (sh~et) 2 of synthetic
material is folded upwardly along a longitudinal center line
such that the edge fold 3 is situated at the bottom and the
free superposed longitudinal edges 4 are situated at the top.
A non-illustrated sealing device provides, transversely to
the longitudinal edges 4, sealing seams 5 at uniform distan-
ces, to thus bond the two superposed web halves to oneanother. Thereafter, the sheet 2 ic fed to a conveying
roller pair 6 which ad~ances the sheet 2 to a cutting device
7 which is synchronized with the roller pair 6 and the
sealing de~ice to sever the sheet 2 in each instance along
the center line of the seams 5 whereby individual bags 1 are
providedO
Downstream of the cutting de~i~e 7, as viewed in the
conveying direction ~, an opening device lo structured
according ~o ~he invention is arranged ~or spreading open the
bags as they pas~ therethrough. The opening device 10 is
formed of one pair of upper suction belts 11, 12 and one pair
o~ lower suction belts 13l 14. The suction belts 11-14 are
each supported by end rollers 15, 16 and 17. The downstream
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end rollers 17 of the lower suction belts 13, 14 are driven
by a shaft 18 from a drive shown as chain 18' synchronously with
the cycle of the cutting device 7 and the rpm of the convey-
ing roller pair 6. The end rollers 17 are situated sig-
nificantly farther downstream than the downstream endrollers lG o~ the upper suction belts 11, 12. The travelliny
speed of the suction belts 11 1~ is yreater than the circum-
ferential speed of the conveying rollers 6, so that the bags
1 are separated from one another as they are grasped by the
10cooperating suction belts 11-14. The facing flights 19-22 of
the two suction belt pairs 11, 12 and 13, 14, respectively,
form, with one another, an adjustable acute angle of maximum
5. The flights 19, 20 and 21, 22 almost touch at their
upstream end at the end rollers 15.
15The end roIlers 15, 16 and 17 of the two superposed
suction belts 11, 13 and 12, 14 are each rotatably supported
on a common carrier 26. The two carriers 26 are, by means of
a rod 27 jointly height-adjustable, for example, by means of
a :thread 27' engaging in a nut 27''. The rods 27 are
coaxial with the upstream end rollers 15. For settlng the
spreading angle, the carriers 26 are pivotal about the rods
27. By virtue of these two measures the apparatus 10 may be
adapted to di~ferent bag configurations. Angle adjustment may
e.g. be achieved by a cross shaft 26a interconnecting the two
carriers 26 and engaging with a right hand and a left hand
thread 26b respectively in a corresponding pivotable nut 26c
(Fig. 3).
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Turning to Figure 3, the suction belts 11-14 are endless
sproc~et belts which have teeth 28 only along opposite
longitudinal edge zones. In the flat mid zone 29 which is
void of teeth, the belts 11-14 have groups 30 of apertures
31. The groups 30 are uniformly spaced from one another; the
spacing between adjoining groups 30 corresponds to the
distance between adjoining conveyed bags 1. In the zone 34
between adjoining groups 30 the suction belts 11-14 are
aperture~free. The end rollers 15, 16 and 17 are sprockets
whose teeth 32 engage into the gaps between the teeth 28 of
the belts 11-14. ~he two coaxial upstream end rollers 15 are
rigidly coupled to one another.
~lso referring to Figures 4 and 5, above the upper
suction belts 11, 12 and bilaterally o~ the lower suction
belts 13, 14 there are secured co~ers 36, 37, 38 to respec-
tive carriers 25. The covers 36-38 serve as lateral guides
for the suction belts 11-14. In Figure 2 the covers are
omitted Por better visibility. Between the covers 36-38
longitudinal suction channels 39, 40, 41 are provided
adjacent the flights 19-22, at the toothed side 33 thereo~.
The longitudinal suction channels 39, 40, 41 are open towards
the fl`ights 19-22. The flights 19-22 sealingly engage the
outer edge faces of the longitudinal walls 42 forming the
channels 39-41. Additionally, support ribs 43 may be
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provided which e~tend parallel to the walls 41. The channels
39, 40, 41 are connected at their longitudinal middle by a
pipe 44 which passes through the carriers 26 and which is
coupled to a non-illustrated suction pump. Thus, as il-
lustrated in Figure 2, the bags 1, as they are advanced bythe circulating, divergent suctio~ belts ll-l~, adhere
thereto by virtue of the suction air stream and are gradually
spread open.
With the short, upper belts 11, 12 there is associated a
respective single suction channel 39 whereas with the long,
lower belts 13, 14 there are associated two longitudinally
adjoining suction channels 40, 41 which are connected each by
a separate pipe 44 with the suction pump. This arrangement
ensures that upon startup of the apparatus, when the leading
bag 1 has first reached the beginning of the suction zone of
the lower suction belts 13, 14, sufficient vacuum could build
up in the channels 40 in spite of the still-uncovered
openings 31 in tha downstream zone.
The described opening device has à very short structural
2Q length and r~liably spreads open the bags, even if they are
made of a very soft, pliable material. The apparatus needs
no mechanical grippers for spreading the bags open. The non-
perforated zones 34 of the suc~ion belts 11-14 have the
advantage that upon suction no significant leakage is
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generated, and therefore the required vacuum may be obtainedwith a relatively small suction output. Further, the non-
perforated intermediate zones ~4 cause a more reliable
opening of the bags l. Were the belts 11-14 perforated
throughout, in case of an only slight difference in the
vacuum between the left and the right channel 39 associated
with the belts 11, 12, the bags 1 would, along their entire
width, adhere to the stronger vacuumized belts 11, 12 and, as
a result, the bags 1 would not spread open symmetrically
which would be disadvantageous for the operation of the
apparatus.
Since, because of the above-discussed reason5, the belts
11-14 should have non-perforated intermediate æones 34, the
belts have to move synchronously w:ith the cutting device 7,
and must not slip as they are driven synchronously by the
shaft 18. Such slippage is prevented by designing the belts
11-14 as sprocket belts.
~ or advancing the bags 1, pairs 48 of mandrels 49 are
mounted on an endless, circulating, non-illustrated conveyor
chain which has ~he same circumferential speed as thë belts
11-14. The mandrel pairs 48 are lowered into the spread-open
bags by means of non-illustrated cam tracks from an elevated
end position in the ~one of the downstream ends of the belts
11, 12 to assume a lower end position ahead of the downstream
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end of the belts 13 and 14. At the same time, the mandrels
49 of the mandrel pairs 48 are moved away (spread) from one
another by means not shown. A gripper 50 travels with each
mandrel pair 49 and, ahead of the end rollers 17, snaps
against one of the mandrels 48. In the lower end position
of each mandrel pair 48 ~he respective gripper ~0 is situated
above the cover 37 but below the longitudinal edge 4 of the
bag 1. The gripper 50 thus clamps the upper bag edge between
itself and the associated mandrel 49~ In this manner the bag
10 1 is held spxead open before leaving the belts 13, 14. The
mandrels 49 do not need to open to such an extent that they
fully open the bags 1. This ensures that in a subseguent
operation the bags 1 may be easily inserted by the mandrels
4g, for example, into a respective cardboard box and there-
lS after filled with material and sealed.
To ensure that the gripper 50 gains access to the edge
of the bag 1 before the bag is released hy the belts 11-14,
the end rollers 17 are situated significantly downstream of
the end rollers 16.
Preferably, the groups 30 of the apertures 31 are, as
viewed in the longitudinal direction of the belts 11-14,
approximately as wide as the mandrels 49. This ensures that
the bags 1 are opened optimally for receiving the mandrels
49. In case the apparatus is to be set for narrow bag
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configurations and for this purpose narrow mandrels ~9 are
used, it is expedient to obtura~e the outermost row of
apertures 31, for example, with a silicone sealing mass.
This also ensures that, in addition to reducing the suction
output, the bags 1 are reliably symmetrically opened. In the
alternative, the entire belts 11-14 may be replaced by belts
having non-perforated intermediate zones ~4 of a different
length.
It will be understood that the above description of the
present invention is susceptible to various modifications,
changes and adaptations, and the same are intended to be
comprehended within the meaning and range of eguivalents of
the appended claims.
