MOULD AND METHOD FOR THE MANUFACTURE OF MOULDED OBJECTS OF PLASTIC

MOULE ET METHODE DE FABRICATION D'OBJETS MOULES EN PLASTIQUE

English Abstract

Manufacture of moulded objects of plastic.
ABSTRACT
Moulded objects of plastic are moulded by the placing of
a sheet, or a layer of plasticified material by suction a-
gainst the outline-forming outside of a mould which is per-
meable to let a gaseous working medium influence the mate-
rial through the material of the mould. Prior to this in-
fluence a mould is manufactured which at least for the out-
line-forming part of the mould consists of a particular
composite material, whose particles are bound together for
the creation of a form-stable exterior structure having air
passages extending to the outside of the mould. The suction
is then carried out on the mould thus created.

Claims

PATENT CLAIM
1. Vacuum mould for the manufacturing of moulded ob-
jects from plastic, which mould is permeable for a gaseous
working medium in order to let this medium influence a
sheet, or a layer of plasticified plastic material through
the material of the mould for by suction to bring the ma-
terial to lie against the outline of the contour forming
mould surface of the mould characterized by at least the
mould surface consisting of a particular composite material
whose particles are bound together for the formation of a
moulding stable outer outline at the same time as they to-
gether define open passages extending through the material
of the mould to the outside of the outline-forming part of
the mould.
2. Mould in accordance with claim 1, characterized by
the composite material being a compound of particles of va-
rious particle size, the particle size being small in the
outline-forming part of the mould.
3. Mould in accordance with claim 3, characterized by
the particles of the composite material being covered with
a layer of binding agents.
4. Mould in accordance with claim 3, characterized by
the binding agent being thermo-hardening.
5. Mould in accordance with claim 3, characterized by
the binding agent containing an adhesion-improving agent.
6. Mould in accordance with any of the claims 1 to 5,
characterized by the composite material having a rounded
outline.
7. Mould in accordance with any of the claims 1 to 6,
characterized by the composite material particles being in
a mutual wedging compound.
8. Mould in accordance with any of the claims 1 to 7,
characterized by the mould having below a basis part in
which the particles are bound together by a real fusion,
while the particles in the rest of the mould are bound to-
gether by a hardening adhesion-compound.

9. Mould in accordance with any of the claims 1 to 8,
characterized by the composite material particles being
kept together by means of a binding agent at such strength
that the mould may be used for subsequent pressing of an
object.
10. Method for the manufacturing of moulded objects
of plastic, as a sheet or a layer of plasticified plastic
material through suction is placed against the outline-
forming outside of a mould which is permeable in order to
let a gaseous working medium influence the plastic material
through the material of the mould, characterized by a mould
being, prior to this influence, manufactured as described
in any of the above-mentioned claims and, at least as re-
gards the outline-forming part of the mould, being built
by particular composite material whose particles are bound
together for the creation of an open, stable structure with
through-going air passages extending to the outside of the
mould and the suction then being carried out on the mould
thus created.
11. Method in accordance with claim 10, characterized
by the use of a particular composite material whose par-
ticles are of such size and shape that they can enter into
a wedging connection with each other.
12. Method in accordance with claims 10 and 11, cha-
racterized by the composite material particles being, prior
to the start of the influence by the gaseous working me-
dium, are bound together by means of a binding agent with
such surface tension that it will attempt to achieve its
smallest surface size.
13. Method in accordance with any of the claims 10 to
12, characterized by the composite material particles be-
ing, prior to the start of the influence through the ga-
seous working medium, bound together by means of a binding
agent which after the binding of the particles leaves a
free, smoothed surface.
14. Method in accordance with any of the claims 10 to
13, characterized by the composite material particles be-

ing, prior to the start of the influence by the gaseous
working medium, bound together by means of a thermo-harden-
ing binding agent.
15. Method in accordance with claim 14, characterized
by the use of a thermo-hardening binding agent containing
a liquable smoothing agent.
16. Method in accordance with any of the claims 10 to
15, characterized by the composite material particles be-
ing, prior to the start of the influence by the gaseous
working medium, bound together by means of a binding agent
which, prior to the final binding of the particles, shows
adhesion-improving properties.
17. Method in accordance with any of the claims 10 to
16, characterized by the suction of the plasticified pla-
stic material on the mould surface by means of a gaseous
working medium being carried out by means of at least the
mould surface being exposed to a vacuum provoking suction.
18. Method in accordance with any of the claims 10 to
17 mentioned above for the manufacturing of moulded objects
of plastic to remove from the on the contour-forming mould-
ing surface of a mould as stated in any of the claims 1 to
9 in accordance with any of the claims 10 to 17 by suction
of a material layer formed object from this mould by means
of an transfer mould being designed to interact with the
side of the object pointing away from the described out-
line-forming outside for the removal of the object from
this outside, characterized by the transfer mould being ma-
nufactured, prior to the removal as described in any of the
above-mentioned claims and being connected with a source
for a vacuum provoking suction and compression air.

Description

2(`S~ 9L?~
The inventlon concerns both a moul~ and a method for
the manufacture of moulded objects of plastic.
The mould is of the kind permeable for a gaseous work-
ing medium in order to l~t that medium affect a sheet or
S a layer of plasticified plastic material through the mate-
rial of the mould in order to bring the material to lie a-
gainst the exterior surface of the out-line forming mould
surface by suction.
The plastic material is pre-heated to a suitable plas-
ticifying temperature and placed on the mould surface insuch a way that it can be brought to lie against the con-
tour of the mould surface by suction, whereafter the object
thereby formed is removed from the mould, e.g. by de-suc-
tion or by blowing.
The object of the invention is to state how this pro-
cessing technique can be performed by means of a mould
which is simple and thus cheap to manufacture so that the
processing technique mentioned will be advantageous to use
also for the manufacture of relatively small series of ob-
jects.
For this reason the mould in accordance with the in-
vention is characteristic thereby that at least the mould
surface consists of a particular composite material whose
particles are bound together for the formation of an out-
line form stable contour and at the same time defining openpassages which extend through the mould material to the ex-
terior of the mould surface.
Such a mould can be manufactured from a both cheap,
inorganic raw material such as sand, and by a processing
technique which is simple, of short duration and thus
cheap.
According to the invention the composite material may
be composed of particles of different particle size, the
particle size being small in the mould forming surface
part. Thereby it is possible to achieve a good passage for
air and at the same time a rather smooth exterior mould
surface is available for the object to be manufactured and

Z~3~ 94
thereby providing a smootll exterior surface of the object.
The mould strength necessary for the carrying out of
the processing process can in a simple way be achleved by
mixing the particles with suitable binding agents, which
may include adhesion improving agents, and that the mould
manufactured from such mixture is hardened e.g. by means
of heat. Also a wedging between the particles may be ap-
plied in order to give strength to the mould.
A suitable composition of the mould consists according
to the invention in that the mould has a basis part below
in which the particles are bound together by a real fusion,
while the particles in the rest o the mould are bound to-
gether by a hardening fusion compound. Such a form presents
a good strength and thus will also be able to sustain sub-
stantial working load.
It is also within the scope of the invention to use
and apply a mould in which the particles of the gravelly
composite material by means of a binding agent are connec-
ted with such a strength that the mould is applicable forthe compression moulding of a moulded object.
The method according to the invention is that prior
to the suction of a sheet or a layer of plasticified plas-
tic material lying against the contour shaping mould sur-
face, which is permeable for a gaseous working medium, amould is manufactured with the characteristics stated a-
bove, in that at least the mould surface is formed by a
particular composite material whose particles are bound to-
gether for the formation of an open stable structure with
air passages extending to the outer mould surface, and that
the suction may then be carried out on the mould thus form-
ed. In this way the total manufacturing process, counting
from the start of the manufacturing of the mould to the de-
livery of the object manufactured may be substantially
cheaper, as it is no longer necessary to manufacture an ex-
pensive metal mould. Therefore it will be possible to apply
the suction technique mentioned above in an economically

2~ 2 ~
attractive way for the production of also small series of
objects, and/or for the manufacture of specially formed ob-
jects.
If for the purpose of binding together a particular
S composite material is used whose particles are of such si~e
and form that they may be wedged together it will at least
partly be possible to avoid using a binding agent.
At another embodiment of the method according to the
invention the particular composite material is linked to-
gether before the start of the suction by the use of a bin-
ding agent having such surface tension that it seeks to a-
chieve the smallest possible surface size. Thus is achieved
that the binding agent - possibly in connection with a pre-
heating - flow together around the particles thus avoiding
a clogging of the air passages between the particles, as
an adhesion will only appear where the particles directly
touch each other. ~n this connection it may be appropriate
according to the invention that the particles have a round-
ed form.
This also means that the permeability aimed at of the
mould can be controlled and adjusted by a suitable selec-
tion of the grain size of the particle material, and dis-
tribution of the grains both in order to achieve favourable
conditions for the adhesion connection between the particl-
es, and for an appropriate dimensioning of the porosity,
in order to avoid undesired pressure drop across a building
material being unnecessarily compact.
The particular composite material may according to the
invention before the start of the influence at the gaseous
working medium be linked together by the application of a
binding agent which after the compound of the particles
leaves a free surface which has been smoothed. This method
ensures an ade~uate surface slip also in cases where the
contour shaping surface due to the already mentioned su~-
face tension effect by the used binding agent for the link-
ing together of the particles results in a free surface
which immediately may seem rough.

;z~3~llz~
In accordance with thr invention the particular com-
posite material particles before the start of the influence
at the gaseous working medium be bound together by the ap-
plication of a binding agent which is thermo hardening.
This has the advantage that the hardened mould may have a
good slip effect towards the model which the contour shap-
ing surface of the mould has been moulded against. Further-
more, the final mould may thereby become temperature stable
to such an extent as to achieve a high degree of freedom
for the cleaning of the mould by the application of heat.
In accordance with the invention a thermo-hardening
binding agent may be applied containing a fusible smoothing
agent. Thus the mould may e.g. be subjected to a treatment
with wax, oil or a teflon product. The fusible smoothing
agent may counter an undesired depositing or detention of
e.g. dust on the outside mould surface. Furthermore, by the
application of heat and suction to a fusible smoothing a-
gent this may contribute to a cleaning of the porosity of
the mould.
In accordance with the invention the particular com-
posite material particles before the start of the influence
by the gaseous working medium may be linked together by the
application of a binding agent, which before the final com-
pound of the particles, presents wedging compound proper-
ties. This may facilitate an easier contour shaping of the
mould surface.
As an example of a thermo-hardening binding agent re-
ference can be given to phenol resin and the wedging com-
pound properties aimed at may e.g. be provided by also ap-
plying silane.
As mentioned at the beginning, the removal of an ob-
ject formed by depositing a plasticified plastic material
on the outline-forming outside of the mould by suction may
be performed in practice by affecting the object by com-
pressed air through the air passages of the mould thuslifting the object free of the mould. If the object is
soft, and for the purpose of removing the object from the

~(3~
mould a transfer mould is usually employed which is adap-
ted for interaction with the side of the object pointing
away from the above-mentioned outline-forming outside for
the removal of the object from this outside and for the
subsequent placing of the object on for instance a conveyer
belt.
It is within the scope of the invention also to form
such a transfer mould from a particular composite stone-
particle material as mentioned above, as the particles of
the material are bound together for the formation of an
open, stable structure with thorough-going air passage to
the outside of the mould and the thus created mould is con-
nected with a source for a suction provoking vacuum, and
for pressure air.
This means that also as regards this part of the total
manufacturing process a cheap raw material may be used in
connection with a production techni~ue which is simple, of
short duration and thus cheap. The hardening time ma~y be
reduced by the addition of accelerators to the binding a-
gent.
A mould used in accordance with the invention can also
be produced in such a way that it may, after use or in case
of heavy wear, be regenerated as the particle-shaped build-
ing material of the mould may be recycled.