Note: Descriptions are shown in the official language in which they were submitted.
THIS INVENTION relates to a method of forming moulded articles
of concrete or the like.
The term concrete or the like shall be taken to include
i materials such as concrete, cement, plaster of paris or the
like material which will harder permanently from a plastic-
like state over a relatively short period of time.
In one form the invention resides in a method of producing
a moulded article from concre-te or the like comprising;
having at least a portion of a mould formed of expanded poly-
styrene; treating the moulding face of the expanded polystyrene
to form a textured and/or pat-terned surface; applying a
coloured composition to the moulding face of the expanded
polystyrene, fi~ing the mould with concrete or the like;
upon the solidi-fication of the concrete~ applying an organic
solvent to the expanded polystyrene to dissolve the polystyrene,
wherein a portion of the solution of the solvent and poly-
styrene is caused to remain on the moulded article, the
amount of solution remaining upon the moulded article being
controlled by the amount of solvent applied to the expanded
polystyrene, permitting the solvent to evaporate from the
solution remaining on the moulding product to form a coloured
glazed finish upon the moulded product.
The invention presents a significant advance over previous
methods of forming moulded articles of concrete or the like.
previous methods have involved the use of bulky, heavy and
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expensive moulds. In addition the form of the moulds are
fixed such that if it is desired to alter the form or
pattern of the moulded article it is necessary to produce a
further heavy mould. Therefore such previous methods were
awkward, expensive and inflexible.
As a result of this invention the moulds used are inexpensive
in regard to their basic material and may be readily formed
to the shape and texture required of the moulded article.
In addition the moulds lend themselves to flexibility in
production since the moulds are produced on a one-to-one
basis with respect to the moulded articles to be produced.
The removal of the mould from the moulded articles by applic-
ation of a solvent reduces the danger of damaging the product
at a stage during which damage is an ever present problem of
previous moulding processes.
It is envisaged that the invention may be used to produce
moulded articles such as flower pots, lamp bases, vases,
decorative sculptured articles and panels. The invention
may also be used in the construction of more massive structures
such as buildings, bridges, tunnels or the like where it is
desired that the exposed surface of the structure has a
decorative coloured finish.
The invention will be more fully understood in the light of
the following description of several specific embodiments.
The descrip-tion is made with reference to the accompanying
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drawings of which.`- !
~ig. 1 is a perspective view of one for~ of
an electric cutting tool which may be used
in forming of the mould; and
~ig. 2 is a perspective view of ano-ther form
of an electric cutting tool which may be used
in the forming of the mould.
One embodiment of the invention resides in the production of
decorative concrete panels for the mounting to the facades
of buildings. The mould for ~uch panels comprises a base
sheet of expanded polystyrene and a border around the edges
to the desired thickness of the final product. The mould
may be formed completely of expanded polystyrene, or may only
have a base of expanded polystyrene, or may be in -the form of
a tray of a non-destructi~le nature into the base of which
a sheet of expanded polystyrene foam may be inserted.
Before installation in the mould the moulding face of the base
sheet is treated to provide a patterned or textured moulding
face. The method of treatment may comprise the spraying onto
the moulding face a small quantity of an organic solvent
which will dissolve the expanded polystyrene (eg. toluol or
petrol3. The amount sprayed should only be enough to affect
the surface of the expanded polystyrene sheet. 9y the use
of the spraying method toge-ther with a masking of the moulding
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face a large variety of patterns may be produced.
Another method of treatment of the moulding face is by means
of electrically heated printing toolsO ~asically the printing
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tools (as seen in Figures 1 or 23 comprise an element 11
shaped to produce a particular pattern upon the expanded
polystyrene sheet. The element is fixed to a support frame
and/or handle 13 by a heat sin~ 15. The element is connected
at either end to a source of electricity the flow of which
through the element will heat -the element. The tool may take
the form as shown in figure 1 wherein the element is shaped
to form a geometric shaped impression in the moulding face.
The shape of the element may be singular like the form shown
in figure 1 or may comprise a multiplicity of shapes to
produce a composite pattern.
The printing tool as seen in figure 2 represents a tool of
a shearing form wherein the element 11 is drawn longitudinally
through the moulding face to produce a grooved pattern on the
moulding face. The tool has a support frame 13 and a heat
sink at each end thereo~ which are to be connected to a source
of electricity. An element 11 is moun-ted between the heat sinks
and may be of any desired shape such that when drawn through
the expanded polystyrene sheeting the element will cut
grooves into the sheeting of the desired shape. The tool
shown in figure 2 comprises a series of substantially U-shaped
loops wherein the termination of each loop is fixed to the
support frame by a screw 17 and washers 19. '~he screw and
washers serve not only to attach -the element to -the support
frame but also act as heat sinks. In use the tools of the form
similar to that shown in figure 2 may be drawn through the
sheet along a straight line, or pivotted about a fixed point
either on the sheet or outside the sheet. r~he support frame
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may also be fixed to a base in order that the sheet is pushed
past the element.
The purpose of the heat sinks is to remove excess heat from
the non-working portions of the element and so prevent burning
out of the element.
Once the moulding face of the base sheet has been treated -to
provide a patterned or textured surface a colouring composition
is applied to the moulding face. ~he application of the
colouring composition may be by any known method howeve~ it is
necessary tha-t the composition contain very little or no
substance which will a-ffect the surface of the expanded poly-
styrene. The colouring composi-tion may comprise spraying
paint having organic solvents in it which is sprayed onto the
moulding face with a very light spray such that most of the
solvent has evaporated from the paint before it contacts the
surface of the expanded polystyrene. Ano-ther method of
application comprises mixing an adhesive used with expanded
polystyrene with a dye or tinting composition and applying the
mixture to the moulding face. An example of the adhesive that
may be used is manufactured by 3M Australia ~ty. ~tdo under
the code EC2296.
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Once the moulding face of the base sheet of the mould has
been textured and coloured in the manner desired the mould
is put together and is filled with concrete or the like
material which is then allowed to set. ~he polystyrene portion
` of the mould is partially removed from the formed article by
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the application of an organic solvent or the like which will
dissolve the expanded polystyrene. The application of the
solvent transforms the expanded polystyrene into a solution
form. The amount of solvent applied to the moulded article
is governed by the amount of polystyrene solution i-t is
desired to retain upon the article and so the desired finish
required of the ar-ticle. If the article ls dipped into a
bath of solvent only a small quantity of -the resultant solution
of polystyrene is retained upon the article and the resultant
finish is a dull glaze upon the coloured surface of the
moulded article. Alternatively if only a small quantity of
solvent is applied to the expanded polystyrene by a spraying
or brushing technique most of the resultant solution of
polystyrene isretained upon the surface of the moulded article.
Upon the evaporation of solvent the resultant finish upon the
moulded article is highly glazed. The transformation of the
expanded polystyrene by the action of the solvent also involves
s~me intermixing with the colouring composition which becomes
at least partially incorporated in the resultant solution of
polystyrene. Such intermixing can produce some interesting
effects on the surface of the moulded article.
A further method of removing the expanded polystyrene from
the moulded article comprises saturating the polystyrene
with an inflammable solvent and then igniting the solvent.
~he heat so produced melts the polystyrene and burns a portion
of it away. However not all of the polystyrene is consumed
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and upon the article cooling the melted polystyrene solidifies
to produce an attractive glaze.
The progress of the invention may be applied to the production
of three dimensional articles having a pat-terned surface
such as flower pots, lamp bases,sculptured decorative articles
and the like. In such a case the inside of ^the mould is
treated in the manner as described for the panels and the des-
truction of the mould is controlled by the amount of solvent
to be applied to the mould.
An added advantage of this method of producing moulded articles
is -that, particularly in the case of panels, the destruction
of the mould from the article can be after the article has
been installed in position. Therefore the mould also serves
in protecting the surface thereof during installation.
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