Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention concerns a method for the manu-
facture of contour-stable objects by the depositing of a
fluidized fibre raw material on a moulding foundation by
suction of a pulp of the fibre raw material on this foun-
dation.
A fluidized fibre raw material means a starting mate-
rial, which may be in wet form, of a fibrous nature and
suited for the manufacture of the desired objects. Such
starting material may for instance be a fibre pulp material
as used for instance for trays and cartons ~or packaging of
fragile and sensitive objects such as fruit, flowers, eggs
and objects of for instance glass. The pulp material usually
consists of a suspended, fibrous cellulose.
It is well known for this purpose to use a production
technique by which the starting material in the form of a
pulp is by a depositing process placed against the outline-
forming outs.ide of a mould which is permeable to let a gase-
ous working medium, through a suction ef~ect, affect the ma-
terial through the material o~ the mould and thus mould the
contour of the material on the mould through suction.
The object of the invention is to indicate how this in
itself suitable production techni~ue may be used not only
to manufacture relatively small and light objects but also
to manufacture larye, rather heavy objects with extremely
high load capacity characterized by a contour stability
which is substantially based on a corresponding thickness
of the material layer deposited on the moulding foundation.
In comparison with this the wall thickness of the said small
and light objects is rather thin and the rigidity necessary
in practice is usually obtained by deliberately moulding the
wall panels which for instance support the said obje~ts as
the walls produce a rather rigid total object by mutually
supporting each other.
According to the invention the stated objective ~s a-
chieved by applying to the foundation a pulp formed by thefIuidized fibre raw material and easily to be drained in
such quantity and by controlling the suction in such a way
that on the foundation is deposited a fibre raw material
layer of such thickness as to provide in all essentials the
contour stability desired for the object by suction.
This will by using the above production technique also
enable the manufacture of elements with high load capacity
such as pallets and building elements which may, contrary
to the said packaging examples, display rather even and
smooth outer surface and which in itself displays a high de-
gree of contour stability. The depositing of a fibre raw ma-
terlal layer of the defined thickness means that the nega-
tive pressure used fox suction may procure a material den-
sity in the fibre raw material layer which is highest at the
outside o~ the material layer directed towards the mould
surface and which will have a reinforcing effect as it is
placed at a distance from the through-going centre plan of
the deposited object.
By using the layer thickness of the object thus manu-
factured the contour stability of this object may according
to the invention also be increased by procuring in the ~iber
raw material layer and distributed over this one or more va-
riations in the layer thickness by correspondingly locallyvarying the suction effect during a joint suction process
for the fibre pulp volume necessary for the manuacture of
the whole object. In this way it will be possible in one and
the same working process, i.e. the depositing of the fibre
raw material on the moulding foundation, to mould both the
final outside desired for the object and, by using the
thickness of the material layer, a contour stability in-
creasing moulded structure in the actual material object
forming the object. According to the invention such a struc-
ture will for instance be able to be shaped as a connectedstructural pattern with a thicker layer thickness compared
with the other parts of the object.
According to the invention a suitable way for the car-
r~ing through of the method is characteristic i.n that~ for
suction of a pulp of the fibre raw material, which is easily
to be drained, in the desired thickness, a mould is used
which at negative pressure is permeable by a gaseous active
working medium and which has a by the working medium per-
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meable mould surface the permeability of which is adjustedto the th.ickness of the fibre raw material layer to be de-
posited by suction of the pulp on this surface.
In this way .it is possible to achieve such interaction
between the draining ability of the pulp and the suction ca-
pability of the mould surface that also elements having
thick fibre layer thickness owing to the desired load ca-
pacity may be manufactured rationally.
In order to achieve local variations in the layer
thickness of the fibre raw material layer of the object, a
mould having a mould surface with a permeability varying in
accordance with the layer thickness of the local variation
or variations respectively or the coherent structural pat-
tern of the easily drainable fibre pulp layer deposi~ed on
the mould surface by suction may be used accordi~g to the
invention.
This means that the depositing of fibre raw material
on the mould surface will vary according to the permeability
of this surface which results in local variations in the
suction effect which, in areas with poor mould surface per-
meability, causes reduced depositing of fibre raw material
in the mould surface whereas the depositing will be high ln
areas with high mould surface permeability.
According to the invention, an embodiment of this me-
thod may be characterized by the use for suction of an easi-
ly drainable pulp of the fibre raw material in the desired
thickness of a mould which at negative pressure is permeable
by a gaseous active working medium which at least as regards
the outline-forming part consists of a partial composite ma-
terial the particles of which are fixed together for theformation of a contour-stable mould surface at the same time
as they together limit passages open to the working medium,
which passages extend through the composite material to the
outsid~ surface of the mould, and that the thickness o~ at
least the composite material layer forming the mould surface
is adjusted according to the thickness of the fibre raw ma-
terial layer to be deposited by suction of the pulp to this
surface.
Such a mould may be manufactured on the basis of a
cheap, inorganic raw material such as sand as well as by
means of a production technique which is simple, of short
duration and thus also cheap. The total production costs of
the mould may be kept at a low level and this embodiment
will consequently be suitable for the production of a s}nall
number of products.
In order to achieve local variations in the layer
thickness of the object's fibre raw material layer a mould
may, according to the invention~ be used in which the com-
posite material formed by the rnould surface has a thickness
that varies in accordance with the layer thickness o~ the
local variation or variations, respectively, or the desired
coherent structural pattern of the easily drainable fibre
pulp layer deposited on the mould surface by suction.
According to the invention a mould may be used the per-
meable mould surface of which is composed o particles with
varying particle size, the parti.cle size bei.ng small in the
part formiIIg the mould surface of the mould and larger in
an underlying supporting layer for this part. In this way
it is possible to procure good passage for air and at the
same time procure for the object to be manufactured a rather
smooth mould outside which will result in the object obtain-
ing an even surface.
The mould strength necessary for the carrying through
of a production process may be achieved in a simple way by
mixing the mould particles with suitable binding agents
which may contain adhesion-improving agents and by hardening
the mould manufactured by such mixture by for instance heat
treatment,. Also wedging between the particles may be used
to give the mould strength.
Furthermore, according to the invention it is possible
to use a rnould having at the bottorn a basic part in which
the composite particles are linked together by a- real fusion
compound whereas the particles in the rest of the mould are
linked together by a hardening conglutinating compound. Such
a mould is characterized by good strength which will also
enable it to resist considerable working pressure.
It is also within the scope of the invention to use a
mould the mould surface of which is shaped with such
strength that the mould may be used for the finishing pres-
sing of a moulded object. Finishing pressing may not only
be used for q~ick removal of water from the pulp layer de-
posited on the mould surface, but also to achieve an espe
cially good material density in the deposited, rather thick
fibre material layer and thus an especially high degree of
contour stability in the final object.
The desired porosity of the mould may be achieved by
an appropriate choice of the grain size and the distribution
of the particles of which the permeable mould surface may
be composed both to obtain favourable conditions for the
fi~ing compound between the particles and for a suitable di-
mensioning of the porosity in order to avoid an undesired
pressure drop across a building material which is unneces-
sarily dense.
The above procedure and mould may as mentioned in prac-
; tice be used for the production of objects of various fibre-
containing suspensions, everything in the presence of the
auxillary materials which may be necessary to create connec-
tion in the material layer obtained by suction onto the
mould.
The removal of an object formed by the depositing of
a fluidized fibre raw material on the outline-forming out-
side of the mould surface by means of a gaseous working me-
dium may in practice be performed place by the object being
affected by compressed air through the air passages of the
mould and thus lifted free of the mould. In practice the ob-
ject will, however, usually still be rather soft and it maytherefore for the purpose of removing the object from the
casting mould be appropriate to use a transfer mould which
is adapted to interact with the side of the object pointing
away from the mentioned outline-forming outside for the~re-
moval of the object from this outside and for the subsequentplacing of the object on for instance a conveyer belt taking
the object to a drying chamber. It is within the scope of
the invention al50 to manufacture such a transfer mould from
a particle composite material as mentioned above by binding
the material particles together for the creation of an
open, stable structure with air passages extending to the
outside of the mould and by connecting with a source for a
suction provoking vacuum.
The transfer mould is producible directly on the basis
of an object produced on the casting mould as on this object
a first auxiliary mould (negative) of for instance gypsurn
is produced corresponding to the side of the object pointing
away from the casting mould and on this first auxiliary
mould ~negative) a second auxiliary mould ~positive) is pro-
duced for instance also from gypsum and the transfer mould
~negative) is then formed directly on this second auxiliary
mould.
The permeable mould surface may be kept clean by, prior
to the start of the depositing process or the transfer pro-
cess, exposing for cleaning purposes the mould surface to
an air current passing through the mould passages for a ga-
seous medium.
A mould used in accordance with the invention and con-
structed by a particle composite material may be manufac-
tured in such a way that it may after use or in case of wear
be regenerated as the particle-shaped building material of
the mould may be recycled.
For the manufacture of a pulp which is to be easily
drained it is possible, according to the invention, as fibre
raw material at least partly to use a starting material con-
taining long fibres which is processed to a pulp partly by
means of a shake-out in a pulper, partly by a preceding, se-
parate, controlled dry grinding by which the starting mate-
xial is divided into dosage amounts and divided into its
fibres whereupon the object is manufactured from the pulp
thus created.
The use of a pulper as an essential step in the proces-
sing of the fibre raw materials for the creation of a pulpfrom which the desired objects are to be manufactured takes
place among other things in cases where the fibre raw mate-
rials are received in the form of dry substances in bales,
for instance as paper waste.
Heavy whirl formation is producecl in the pulper by
which the single parts of the material rub against each o-
ther and is thereby pulverized and the raw materials divid~
5 ed into fibres.
Especially in case of heterogeneous material such as
waste or recycled paper it has to be anticipated that this
separation is carried out successively so that the fibres
released first are exposed to a higher degree of additional
substantial processing than the fibres released later. In
other words the processing in the pulper will in its pro-
ceedings thus be uncontrolled and thus heterogeneous. The
said additional processing results in an increase in both
the degree of grinding (QSR-Schopper-Riegler) and thus the
formation of mucus in the pulper, which negatively affects
the subsequent draining of the object manufactured from the
pulp and increases the shrinkage of the object during drain-
ing and drying of its material.
The method according to the invention achieves that to
the pulper is at least partly added a fibre raw material the
fibres of which are already to a substantial degree sepa-
rated into single fibres why they are more instant and at
the same time susceptible to the self-grinding effect and
mixing effect obtained ln the pulper. As the pulper proces-
ses a more uniform raw material also the grinding degree ob-
tained in the pulper through self-grinding may be adjusted
to be more uniform and the above-mentioned binding of water
in the pulp leaving the pulper will thus be more control-
lable.
The same procedure will, however, also result in other
advantages which are especially valuable in case of recyc-
ling of paper waste.
Recycled paper waste exists in many different qualities
and gradings. If this material prior to the shake-out in the
pulper is exposed to a separate, controlled dry grinding,
it is often possible to use a poorer and thus cheaper mate-
rial quality, than if the division process was only carried
out as a shake-out in the pulper.
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the preceding separate dry grinding as mentioned above as
a multiple-stage process whereby it is possible to separate
the starting material in dosage amounts in a special effi-
cient manner.
In this particular way also e.g. was~e paper material
containing plastic, water resistant paper, plastic laminated
cartons and paper, to the degree desired can be separated
into fibres and other particles. Separated constituents not
being paper can be screened off before entering the pulper,
or it is possible to let these constituents since they exist
in pulverized form enter into the following production pro-
cess.
At a performance of the method a long fibre starting
material having ~een subjected to a separate controlled dry
grinding be added to an already in the pulper foxmed pulp
and be subjected to a joint time-limited shake-out with
this.
In this manner an object can be manufactured whose
fibre material is partly mainly bound by hydrogen fibre bin-
dings partly have been mixed with air suspended fibre mate-
rial for whose binding glue is normally used. It has turned
out that in this way it is possible to abandon a traditional
complete hydrogen binding of the whole pulp, which means
that the drain and thereby the production time for the ob-
ject can be substantially reduced. Furthermore the methodmakes it possible to obtain a strict control of the desired
object strength characteristics as it will be possible to
have strict control of these by the addition o~ glue.
These advantages are of major importance for a rational
and thus economic industrial manufacture also of large, form
stable objects by the application of the suction technique
described.
It will e.g. be possible to carry out a multiple-stage
dry grinding by the application of a tearing machine also
called a shredder followed by a treatment in a hammer'mill
which thus can receive the material from the shredder in do-
sage amounts and which exposes the material to a further
grinding process before it if required also in special do-
sage amounts is added to the pulper for the actual shake-out
processing.
The separate, controlled dry grinding suggested accord-
ing to the invention of the fibre raw materials prior to
their shake-out in the pulper also prov:Ldes the possibility
for the co-application of recycling waste paper in cases
where the objects to be manufactured must be shrink proof
and measure proof. A starting material with a high content
of wooden fibre causes less shrinkage that if the fibre were
cellulose fibre. It has turned out that by applying the me-
thod according to the invention it is even possible to add
to a wooden paper raw material a substantial amount of cheap
recycling paper including carton waste which not necessarily
is wooden since it is possible to manufacture due to the
preceding separate controlled dry grinding of the raw mate-
rial a pulp which causes no undesired shrinkage of the ob-
jects manufactured.
It is a well known principle for the manufacture of ob-
jects of a fluidized fibre raw material to utilize auxiliary
materials such as f illing material and chemicals and binding
agents. The auxiliary materials decide whether the objects
manufactured shall be more or less strong, hard or transpa-
rent, or weak, soft and absorbing. The present invention is
also advantageous in connection with the application of such
auxiliary materials.
The division of the manufacturing process in multiple-
stages actually increases the possibility of adding ~he
auxiliary materials at different stages of the total manu-
facturing process. The achieved open structure of the final
pulp, obtained as a result of this particular lnvention,
even facilitates a better access ~or auxiliary materials so
that e.g. a binding material may be applied more or less in-
tegrating on the surface of the objects in order to increase
the strenght of the wall. The addition of auxiliary material
under the preceding separate, controlled dry yrinding will
in a especially good manner be ahle to further a particular
unifo~m distribution of the auxiliary materials in the ma-
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nufac'ured fibre mass. It is of course also still possibleto add the auxiliary materials to the pulper.
Furthermore, it lies within the scope of the invention
that the shake-out in the pulper is carried out as a manu-
facturing process dependent on the preceding separate, con-
trolled grinding. In other words the obtained degree of
self-grinding in the pulper can be adjusted in accordance
with the degree of the grinding which according to the cir-
cumstances has been carried out at the preceding dry grin-
ding stage(s). As an example, a paper pulp which in the pul-
per is separated into a normal, at self grinding obtained
grinding degree of 600 SR (Schopper-Riegler), be added dry
grounded fibre material whereafter the mixture is processed
in the pulper ~or 5 minutes more. Objects manufactured from
such a mi~ture pulp may be provided with a special heavy
thickness, porosity and permeability. That means that the
products can have good drainage qualities and therefore also
can be manufactured with large wall thickness.
An easily drainable pulp manufactured according to the
invention facilitates unproblematically a uniform addition
of the fibre suspension over the mould even in cases of
manufacturing objects with large wall thickness.
Waste paper, also called return paper, may be very com-
posite, and contain fibre with a large variety of fibre
2S lengths. However, it has actually turned out that the ave-
rage ibre length is so large that the above mentioned ad~
vantages especially as regards drainage and structure may
be obtained when this paper matexial forms part of the ma-
nufacturing process.
The method according to the invention will also be a-
~ vailable for the processing of so-called virgin ma~erial.
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