Note: Descriptions are shown in the official language in which they were submitted.
~9295
Process for the production of thick walled shaped articles
especially for packaqina uses.
The invention relates to a process and a suction mould for
producing thick-walled shaped articles, having particular
application to packaging.
Process and suction moulds for the above mentioned purpose are
known in the art, an example of which was featured in the Paper
Trade Journal of 13/11/1953, pages 175-180. This prior art
process and the corresponding suction forms permit production
only of relatively thin-walled and thus relatively soft, shaped
articles which are therefore somewhat unstable. Such shaped
articles, especially those having thin walls, need to be
specially dewatered and dried immediately following the suction
moulding step. Although such conventional shaped articles can
serve as egg boxes or shell-like fruit and vegetable containers
and meet the strength requirements of that role, they are not
suited to replace shaped articles made of polystyrol, which must
be used for packing heavier objects such as machinery, or machine
parts that must be immobilized for shipment inside a packing
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carton. It would, however, be suitable from an environmental
viewpoint if such replacement were possible. For this reason,
therefore, machines, machine parts or even wine and champagne
~ bottles, are packed in form-fitting polystyrol shaped articles.
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Only with such packaging articles is it possible to ship the
objects in the carton without danger of shifting or breakage.
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Shaped articles comprising light and environmentally friendly
degradable fibrous material have, until the present, been
prevented from effectively replacing polystyrol shaped articles,
because the raw material used in producing such shaped articles
can only be produced with limited wall strength, which, because
of low inherent stability when wet, cannot be removed immediately
following the suction-moulding stage. Although rapid removal of
the moulded articles would serve the efficiency of the moulding
process, the thin cardboard walls could not prevent sliding or
breakage of the packed objects during shipment. Prior art
examples of such moulded articles have been disclosed in U.S.-A-3
016 177 and 3 315 450. These however, produced from a fibrous
pulp mash, have thin walls (to a maximum of 3 mm) and thus
required a very pronounced ribbing structure for stiffness.
Until now, it seems that shaped articles made from fibrous raw
material could only have thin walls because the suction bed of
the conventional suction moulds plugs up too rapidly which,
despite continuous vacuum pressure being applied to the suction
form, prevents further accretion of wet fibre material along the
walls of the mould. This prevents both formation of thicker
walls and creation of a durable bond with the raw material
already sucked onto the sides of the mould.
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The object of the invention, therefore, is the improvement both
of the prior art process for suction moulding and the suction
moulds that are used to produce shaped articles of adequate wall
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thickness from shredded waste paper and/or cardboard. ~he
proposed process and apparatus enable production of an article
having greater stability while permitting its practically
; immediate removal from the suction mould.
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The object of the invention is satisfied by a prior art process
of the type mentioned above, wherein suction applied to the
suction moulding apparatus through a plurality of separate holes
provided in the suction surface and through at least one bed
located in front of the suction surface serving to permit
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suctional flow via mesh apertures that are smaller than the
apertures, suctions raw material held in a suspension and whereby
furthermore the suction mould used according to the invention
comprises a suction surface having a stable frame provided with
holes that are separated from each other and distributed over
such surface and whereby, furthermore, the frame is covered on
the side facing the moulded article deposit with a bed having
fine mesh apertures such as net, wire or woven meshing, the size
of whose apertures is smaller than the cross section of the holes
in the suction surface. Advantageous and practical alternate
embodiments of the invention will be described later in greater
detail.
The expression "approximately", which appears in the subsidiary
claims, is used in the disclosure because the actual limits
cannot be precisely defined. It will be appreciated in this
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respect that t is unavoidable to have precise data on the
dimensions of the raw material to be processed since such
material is, prior to processing, not shredded to correspond to
the dimensional variations of differently shaped articles. This
relationship can have a variety of results when the raw material
is placed in suspension.
It was surprising to note that use of the process according to
the invention in conjunction with the specially-designed suction
form permitted production of walls whose thicknesses were double
that of conventionally-moulded articles. In addition to which,
the shaped articles produced by the process according to the
invention could not only be removed immediately from the suction
moulding apparatus, but, when dried, exhibited the stability
required to serve as a replacement for polystyrol packaging
articles which had, up to now, been used for packaging purposes.
It is crucial to the operation of the invention that suction is
no longer applied directly through a finely-meshed suction
surface whose apertures can become clogged. In the apparatus
contemplated in the invention, the raw material in suspension
flows through a frame having relatively large holes and at least
one suction flow-through bed whose mesh size is smaller than the
size of the holes contained in the frame. The very surprising
effect achieved with the apparatus according to the invention,
which is to produce by means of suction a product having thicker
walls, can be explained in part by the emergence of cross suction
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between the frame and the finely meshed suction flow area. It is
believed that such cross flow permits the suction to act for a
longer period of time on the deposited raw material. The result
of this arrangement is that, in general, thicker material
deposits are produced, which could not be produced either with a
frame containing alone or with a finely meshed sieve-like mould.
Another salient feature of the apparatus according to the
invention is a stable frame that permits the application of
vacuum pressure to the mould, which permits the material
deposited on the sides of the mould to be thicker.
At the end of the suction step, vacuum pressure is maintained for
a certain length of time to allow the moulded article to be
dewatered at least to some extent. Due to its thick wall and
despite the water remaining in the raw material, the moulded
article is basically stable enough to permit its removal from the
suction form prior to complete drying while retaining the
originally intended shape. In addition, the increased thickness
of the walls of the moulded article provide the latter with a
degree of stability or stiffness that enables the article to
effectively replace conventional shaped articles produced from
polystyrol.
One obvious advantage of the process according to the invention
is that waste paper and/or waste cardboard board can be shredded
without further preparation. In other words, the shredded waste
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material is merely added to the suspension liquid, in which it is
softened; the resulting liquid is then transferred without
further modification to the suction moulding process.
It is irrelevant in this respect whether or not isolated pieces
of plastic sheeting or film become mixed with the waste, even
though such plastic is often found mixed in with paper and
cardboard waste. It has been demonstrated that the presence of
plastic shreds in finished moulded articles can even be
advantageous since their presence serves to increase the rigidity
of the formed articles, although it is not advisable that the raw
material used contain more than 5~ of plastic scraps.
Although the main advantage of the process according to the
invention is the ability to process shredded raw material and to
produce moulded articles of greater wall thickness, it is also
possible to preprocess paper waste into single fibres and to use
such fibres, or, for example, wood shavings, in the raw material
suspension.
As has been demonstrated, it is not absolutely necessary to add a
bonding agent to the aqueous shred suspension, since it has been
found in every case that sufficient crosslinkage of the shredded
material occurs during the suction phase, which then later
imparts to the finished shaped article a sufficiently stable
internal structure. In addition, the raw material used for
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processing usually contains a percentage of bonding agent that is
released into solution when placed in suspension. If bonding
agents are to be added to the suspension, it is adv~sable to use
those compounds that are normally used in paper making.
Examples are: a boiled soda solution, i.e., caustic soda,
saponified resin, phenolic resins, montanic resins, or resins
derived from cellulose liquors. Also suitable are paper-making
resin, bonding casein, starch, animal glue, sodium silicate, or
similar substances.
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The process according to the invention, the suction mould to be
used in conjunction with the process, and further advantageous
and practical alternative embodiments of the invention will next
be described in greater detail by means of the following drawings
of embodiment examples.
Schematically shown are:
Figure 1. a greatly enlarged section of the suction surface with
a corresponding section through the raw material being
~ sucked dry to form the moulded article;
; Figure 2. shown still larger is a section through the suction
surface which has been designed as proposed;
Figure 3. a plan view of the suction surface viewed from the side
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upon which the raw material is deposited;
Figure 4. a section through a suction box;
Figure 5. a section through a special design of a suction box;
Figure 6. a view of a moulded article as seen from the side on
which the raw material is deposited:
Figure 7. a section through the moulded article shown in Figure 6
in connection with an obiect that is to be packed;
Figure 8, 9.
special embodiment examples of the suction surface in
section;
Figure 10 a perspective view of a section of an embodiment
example of a moulded article; and
Figure 11 a flow chart of the process.
In Figure 4, the proposed suction form comprises a suction box 1,
provided with a vacuum or low-pressure connection 2, and a
suction surface 3 corresponding to the desired shape of the
moulded article VS. If, as illustrated in Figure 4, suction box
1 is provided with a cover 9, such cover possesses an inflow
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connection 10 of a diameter capable of permitting the raw
material suspension to flow into the mould cavity when the entire
mould box 1 is immersed in the suspension. In order to be able
to produce moulded articles VS having a wall thickness S of at
least 4 to 6 mm by using such a suction mould, the special design
of suction surface 3 shown in Figure 1 must comprise a frame 4
having a stable shape and separate holes 5 that are distributed
over the suction surface (also see Figure 3). In this
arrangement, frame 4 is covered on the side on which moulded
article VS is to be formed with at least one finely meshed bed 6
comprising netting, wire or woven material (e.g., of nylon) the
mesh apertures of which are significantly smaller than the cross
section of holes 5. In this special embodiment, the holes have a
diameter D between 1 and 2 mm, preferably 1.5 mm and are
separated from each other by a distance A of from between 4 and 6
mm, preferably 5 mm. It is preferable if a copper wire mesh be
used for bed 6 and have a thickness of between 0.2 and 0.4 mm
whereby wires 7 comprised in the mesh are separated from each
other by a distance A1 which is between 0.3 and 0.5 mm. A
particularly advantageous and effective arrangement comprises
that the interwoven wires 7 of the finely woven bed 6 extend over
two planes E as illustrated in Figure 2. It will be appreciated
from the enlarged illustration shown in Figure 2 and highlighted
with arrows that cross flows are produced to a certain extent in
bed 6. Such crossflows are clearly responsible for increasing, as
necessary, the depth of the layers of the suspended raw material
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deposited on bed 6, a result previously unobtainable by using
conventional processes involving use of a relatively thin sieve-
like sheet that permitted use only of a limited vacuum pressure
and which accordingly clogged very quickly and thus prematurely
limited the amount of material that could be deposited. Of
course, several very thin beds 6 can be arranged one on top of
the other, whereby the thickness of each individual bed is only
approximately 1 mm. Bed 6, in addition, should not comprise a
thin sheet having only holes, because such a sheet would be
unable to facilitate the creation of cross flows. If bed 6 is
designed to comprise a plurality of layers (see Figure 8), the
mesh width of the individual layers can even be equal to or
nearly equal to the diameters of apertures 5, because the depth
of the layers causes the apertures in bed 6 to be somewhat
staggered. Depending on the choice of material used for bed 6,
for example, one or more beds 6 can assume the role of frame 4,
i.e., replace the latter, in which case bed 6' located on the
suction side would come into contact with the moulded article via
its fine surface structure. A precondition to such a design is
naturally that the material used for bed 6 has a stable shape,
i.e., a soft textile weave should not be employed.
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- Although it is preferable that form-stable material be used in
bed 6, it is also possible to use a material of unstable shape
which would allow bed 6 to be pressed into the shape of frame 4
by means of equipment and be mounted on frame 4. The plan view
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11
(shown in the direction of arrow P, as per Figure 2) shown in
Figure 3 corresponds to the dimensions of an actual practical
embodiment, wherein holes 5 have a diameter of approximately 1 mm
and whereby the mesh size of bed 6 is from 2 to 4 times smaller
than apertures 5 and whereby furthermore, flat F and strip-shaped
waste material SA are as shown held in suspension. Flat waste
material, strips for example, have in this arrangement a size of
approximately 1 to 6 cm2 which produces the best results. Strip-
shaped waste material, i.e. waste material having the appearance
of sauerkraut, which is produced by shredding office paper, are
approximately 1 to 5 mm wide and approximately 10 to 30 cm long.
Suction surfaces 3 comprised by mould box 1 shown in Figures 4
and 5 are shown in their most basic form. Further and
significantly more complex mould designs of frame 4 and
corresponding bed 6 are easily obtainable, the only precondition
being that no zones exist in which suction beds mutually block
each other off, the result of which could be to prevent the
deposit or suctioning of raw material particles.
Production of more complex mould designs and the ability to mould
simple articles, can benefit from a suction mould F comprising
two parts, whereby mould sections F1 and F2 designed so as to be
able to separate from each other. In a basic configuration of
mould box 1, as illustrated in Figure 4, all that is required is
a constructed hinge 14, which allows the upper part 9 of the
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12mould to swing open. It is also possible, especially for more
complicated moulding box designs, as shown in Figure 5, to
provide vertical guides 15, by means of which the upper part can
be raised. It has already been demonstrated that the finished
moulded packaging article is, due to its increased wall
thickness, entirely capable of withstanding, i.e. will not tear
apart in the presence of loads produced when the form is pulled
apart. The increased wall thickness that can be obtained by
using the process according to the invention also affords the
advantage of moulding with the aid of moulds that can be pulled
apart. In the mould versions shown in Figures 4 and 5, the
provision of covers 9 provides the moulded articles with clean
edges.
The novelty of the design of suction mould F, as shown in Figure
5 owes to the fact that arranged in mould F on the suction side
is at least one further suction surface 3' comprising a separate
suction box 1', whereby suction box 1' is provided with a
separate suction connection 1''. The additional suction surface
3' is in this arrangement arranged to function in conjunction
with the other suction surface 3 located at a distances D1 from
nearby zone 8, which corresponds to at most approximately double
the wall thickness S of the articles VS that are to be moulded.
This arrangement permits moulded article VS to be provided with a
stiffening rib arrangement 11, which contributes considerably to
increasing the stability of moulded article VS, particularly in
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13
the relatively wide edge regions 12. In this connection,
reference should be made to Figures 6 and 7, for example, wherein
Figure 6 shows a view of a finished moulded article VS from the
unsmoothed side, while Figure 7 shows a section through the same
moulded article. Figure 7 also shows two such moulded articles
being used to immobilize an object G which is to be packed inside
a carton K. The mould cavities 13 are, as indicated in Figure 6,
formed in this design by the suction surfaces 3' which are
provided additionally in mould F, and have a corresponding shape;
this is shown in Figure 5.
It is very important that the spaces separating holes 5 of frame
4, permit formation on one side of the holes of a suction cross
section whose size is sufficient to increase material thickness
while on the other side of frames 4 allows enough stability to
prevent the frame from deforming under high vacuum pressure (e.g.
120 millibar). In the arrangement of the apertures, the spaces
separating the holes in the frame can vary greatly since these
depend on the size of the aperture, the material from which the
frame is made, the wall thickness of the frame and lastly on the
material used to produce the finely meshed bed 6 that is applied
directly over the frame 4. Furthermore, the distances between
the holes (for example, corresponding to the diameter of holes 5)
also influences the thickness of the finished moulded articles.
Figure 11 shows the flow chart for the basic configuration of the
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overall process. Waste paper 16 is reduced in a shredding
machine 17 to the required particle size and then transferred to
a mixing tank 18 into which a sufficient quantity of suspension
fluid is pumped from a tank 19. This fluid, together with the
particles which it contains and which become softened by such
liquid flow into a proce~sing bath 20, into which the mould boxes
1, which are fitted with a raising mechanism 21 are immersed.
Mould boxes 1 are connected via a vacuum line 22 and a pressure
sealed separation vessel 23 to a vacuum pump 24 located on the
side on which suction is applied. The suctioned fluid is pumped
by means of a pump 25 from container 23 back into tank 19 from
which point it recirculates through the system. As indicated by
the broken line, all tanks and containers are provided in double
and are connected inside the system. The main purpose of this
double arrangement is to allow sufficient time for the waste
particles which have been poured into the mixing vessels
containers to be softened while the moulding process continues
without stoppage.
Configuration example:
Reference is made here to Figure 11. The paper shreds which have
been produced from waste paper 16 with the aid of a shredding
machine 17 are geometrically undefined, but have an average size
ranging from 1 to 6 cmZ. Approximately five hundred litres of
liquid containing approx. 3 to 5 kg of waste paper particulate,
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is poured into the mixing vessel and agitated. The temperature
of the liquid in the mixing vessel corresponds to ambient
temperature, i.e. the temperature of the transfer lines, but can
be raised if the particular characteristics of the waste paper
; particles being used so require. In the present example, the
finished dry weight of the moulded article is approx. 200 g which
corresponds roughly to a moulded box of approximately 400 x 400 x
150 mm3. If the vacuum pressure applied to suction box 1 is
approx. 120 mb and the required thickness of the article wall is
approx. 5 to 6 mm, the suction phase lasts approximately 3 to 5
seconds. The moisture remaining in the moulded article depends
on how long the vacuum pressure is applied to moulding box 1,
after the latter has been withdrawn from the suspension in the
immersion bath by means of raising mechanism 21. After being
removed from moulding box 1, the moulded article or articles are
dried inside a dryer 26.
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