Note: Descriptions are shown in the official language in which they were submitted.
~0131~
--1--
:.
Manufacturing plaster elements
The invention relates to a process and an apparatus for
manufacturing plaster elements with decorative high quality
surface finish which are widely used in the building
industry. The plaster elements can be made of a single
colour or marbled in various configuration3, for example as
flat or relief-like plates, as corner or column elements or
as figurative bodies.
Endeavours have been made for a long time to produce
10 , plaster elements of high strength, particularly in the
surface area, and with a highly decorative effect. Various
methods of producing such plaster elements are known:
- Use of high-quality plaster
Supply of little mixing water and addition of
chemical products which increase the flowability
- Mechanical stirring
- Supply of smaller~ amounts of mixing water and
shaplng through mostly briefly applied high
pressures using presses, rollers and pressure
~ `oelts
- Sucking~off the excess water (DR-PS 99384)
- Applying a layer of powdered plaster onto a wet
layer DE-PS 1203655).
With~most of~these processesj a water-plaster ratio is used
where the proportion of water is above that which is
required in order to~ allow ~the chemical procéss of
recrystallisation during the setting process.
The water and air inclusions are only removed to a small
extent from the moulded mass before the setting process so
that the proportion of pores in the finished plaster
element is relatively high and the visible surfaces do not
have a high-quality surface f1nish.
.
2 ~
--2--
Similarly the process for removing excess water from
fréshly-set plaster bodies according to DE-AS 1771866 does
not lead to a reduction in the pore space nor to high-
quality surface finishes.
'
It has indeed already been attempted to make waterproof
tiles from plaster ~DE-OS 3327336; DE-OS 3318364)
;~ According to this process, an aqueous sludge paste of
alpha-gypsum semi-hydrate, sulphate foundry cement and
aluminium sulphate are introduced into a plate-like casting
mould, defoamed during setting by applying vibrations, and
then removed from the mould after the setting process. The
; cast.ng mould which is open at the top comprises a base
plate with divisible edges which are detachably connected
- together. To speed up the process several mixing
;~ ; 15 containers can be connected to the individual moulds by
~ swivel outlets. The plaster tiles can be provided with a
-~ surface coating. To increase the strength it is proposed to
introduce inorganic and/or organic fibres into the tensile
zones of the tiles. It is hereby seen that the vibration
~20 of~an aqueous plaster sludge in a mould with smooth pore~
free inner surfaces is not sufficient to produce visible
surfaces with a~high quality finish.
~ ::
When making stucco marble particularly high demands are
made of the visible surfaces.
`In addition to pore-free surfaces which are capable of
being polished, strength is~also of decisive importance for
these products in order to ensure wide usage.
According to DE-PS 808 033, after preparing and applying a
coloured structured design layer on a support layer in a
specific sequence with special materials and special tools,
grinding, smoothing and polishing processes must be
.
: '~0~31~:L
-3-
:
repeated seven times and more in order to achieve a hard
dense surface similar to natural marble. Even when using
mechanical grinding processes which are only possible with
flat surfaces, the expense is still very high.
In the process for manufacturing plate~ and other products
~ with marble-like appearance ~DE-AS 2 750 702), calcium-
-~ containing binding agents with a certain speci~ic surface
are brought to set together with catalysts with or without
the application of pressure. After setting, grinding,
cementing and polishing is likewise required.
.~ ,
The process for manufacturing an ~object of stucco marble
according to DE-OS 2 905 609 proposes pouring Plaster of
Paris paste or fluid into a hollow mould which has a smooth
hard surface from which the object is removed once set.
This process does indeed reduce the laborious grinding,
smoothing and polishing processes but has similar drawbacks
regarding the quality~of the finished surfaces. Expensive
assembly processes are required for this type of object.
The aim of the invention i8 the industrial low-cost
manufacture of plaster elements having decorative high-
quality~surface finishes.
; In the~ process of the present~inventlon,- a multi-layered
moulding mass consisting of~plaster and~water is shaped in
a mould under pressuré, and the process comprising the
i 25~ steps of
`~ placing a layer of uniform thickness of a water-plaster mixture on a~pore-free smooth~mould~base,
placing a layer of dry plaster powder of uniform thickness
on this mixture, ~ ~
covering the moulding mass with a hygroscopic and/or open-
pore material,
:
:
, ,, ~",. ~ ",
., ~ ,. ., -,
r~
-4-
~; pre-compacting the moulding maas through pressure elements
: with simultaneous air extraction,
compresslng the moulding mass with air exclusion,
building up an excess pressure in the moulding mass and the
material covering same,
allowing the plaster part cles in the flowable layer of the
moulding mass to migrate towards the mould base 80 that
they concentrate at or near the mould base and allowing the
constituent parts of the moulding mass not required for
recrystallization such as air and excess water to migrate
towards the pressure elements so that they concentrate in
;~ the layer of plaster powder and predominantly in the
material covering the moulding mass
`~ maintaining the pressure elements at least partially
pressurised until the plaster elements reach a stable
shape, and
removing the plaster element from the mould with the aid of
the pressure elements.
Using the invention, it is possible manufacture more
20 particularly marble like plaster elements with high-quality
: surface finish wherein the plaster particles are
: concentrated in the :area of the visible surfaces of the
plaster element so that a high degree of coalescence of the
crystallizing plaster particles arises, a simplè loading of
the apparatus~with~the mixture ingredients-and demoulding
~; of the plaster element:from the apparatus is possible and
`~ a subsequent expensive:surface finishing treatment is no
~ longer required.
'?: ~ ~
Also accordlng to~ the: invention to manufacture more
particularly marble-like plaster:elements with high quality
-~ surface finiæh wherein a~ multi-layered moulding mass
comprising plaster, water and if necessary colour pigments
is shaped in a mould under pressure, first a layer of even
thickness of a flowable water-plaster mixture is placed on
.:
: ~
- ~O:L31~1
; :
-5-
`~ a pore-free smooth mould base and then an evenly thick
layer of dry plaster powder is placed on this mixture. The
even distribution can be helped by a short stirring
process.
''~
Directly following this, the moulding mass is completely
covered with a hygroscopic and/or open-pored low-
cvmpressible material, precompacted by rigid and/or
flexible pressure elements with simultaneous air
extraction, and then compressed with the exalusion of air.
I0 An excess pressure, preferably between 0.13 MPa and O.S MPa
is built up in the moulding mas8 and the material covering
~; same, wherein this excess pressure can be increased
continuously up to a predetermined value or built up
suddenly. ~he size of the excess pressure and the time for
which it is maintained depend on the moulding mass and/or
; the intended shape. The air-tight closing of the moulding
` mass in the side areas between the pressure element and
mould base can be produced by the setting moulding mass
itself.
-~ ~
~,
It has proved particularly favourable if the excess
pressure is built up in~the closed mouId. This has the
additional advantage that the entire moulding mass, even
the peripheral;areas,~is exposed to the excess pressure in
the;~same way. The work step up to the build-up of the
excess~pressure have to follow without delay. Through the
~- pressure expansion in` the closed mould, the plaster
particles of the flowable layer of the moulding mass are
transported towards~the mould base where they concentrate
at and near the subsequent visible surface of the plaster
element which is being moulded. At the same time, the
ingredients o:E the moulding mass~which are not required for
recrystallization, such as air and excess water, ~are
transported ln the mould towards the preesure elements and
concentrate in the layer of plaster powder and more
.
20~31S~
_f~_
particularly in the material covering the moulding mass
At the end of this concentration process, the pressure
elements remain at least partially pressurised up to the ~`
end of the setting of the plaster powder layer so that no -~
undesired distortion of the plaster element occurs. The
plaster element is then demoulded by means of the same
pressure elements.
~,~
;`Surprisingly the visible surfaces o~ the plaster element
have a high-quality surface finish. f~he work steps carried
out according to the claimed process in the described
sequence and under the said conditions lead to an effect
;~which is against expectation so that except for a simple
polishing no further processing of the visible surfaces is
required. Also the compression of the moulding mass in the
mould ~with the~ exclusion of air is to be regarded as
unusual since constituent parts such as excess water and
air pockets are still present in the moulding mass which in
processes known hitherto are pressed out from the moulding
mass through pressure but here are diverted into the
covering materials.
By~adding colour pigments into ~the flowable water-plaster
mixture~or directly into the mould the~solution according
to~the invention can be used for the effective industrial
production~of stucco marble.
Since the water-plaster mixture is flowable, the colour
- ' pigments can ~e well m;ixed into the mixture in order to
achieve a desired~marbled colour structure. The water-
plaster ratio of the flowabl~e mixture should be about 0.79.
PIaster powder is~then evenly distributed in the flowable
~`~30 mixture to the extent that the~water-plaster ratio of the
total moulding mass, comprising flowable mixture and
plaster powder, amount to about 0.25.
'.
,-,.
f
~L31~:l
.~ -7-
. : . ~
The apparatus according to the invention ~or manu~acturing
~: plaster elements consists of a lower part movable within a
`:~ housing, with a smooth pore-free mould base and with side
walls which form mould walls, an upper part in the form of
a recess, the upper part being movable vertically towards
the lower part, means for locking together the lower and
upper parts, pressure elements for pressing the upper part
towards the lower part and a load distribution plate which
~-: completely covers the inner configuration of the frame and
is placed between the upper part and lower part.
:,
.~
:~ For manufacturing more particularly marble-like plaster
~ ~ elements with high-quality surface finish, the invention
~; also provides apparatus comprising a lower part which holds
the moulding mass and which has a smooth pore-free mould
lS base and side walls, and a pressure-biassed upper part
which moves vertically towards the lower part and can be
locked therewith is characterised in that the upper part
.~ and lower part are brought into connection with an
abutment, the upper part is designed as a recess with
. ~ 20 pressure elements attached for articulated movement to the
top and bottom wherein the pressure element attached to the
top is supported~on the abutment whose end face facing the
lower part contains a protruding peripheral elastic seal,
the lower part consists of a stable-shape frame with
integrated partition: frame wherein the lower part is
supported air-tight on the mould~base through the elastic
seal fitted into the end face of the frame facing the mould
i base, the mould base is mounted movably on the abutment and
~: that;a load.distribution plate which completely covers the
- 30 inner configuration o~ the partition frame is inserted
-~: between the upper part and lower part. This load
: distribution plate can also be connected to the pressure
: element on the side of the base.
~::
~8-
The upper part and lower part can be locked together in
~; air-tight manner through a seal. The air outlet can be
integrated in the recess and as the pressure increases in
the pressure element can be closed by same.
Several pressure elements can be mounted on the recess.
The pressure elements are cushions which are coupled
together in technically controlled manner and which can be
biassed by pressure.
:
The end faces of the partition frame adjoin the mould base -
with their sharp edge.
~,
The facing side faces of the frame and partition are wedge-
~; shaped corresponding to each other.
:~i
~ ,
During shaping the partition is held locked in the frame
;~ but during demoulding the partition is movable in the
frame. The side of the mould base facing the moulding mass
~-; can be smooth or structured.
,
The load distribution plate preferably has a sandwich
construction. The top layer is a support layer for the
actual transfer of pressure and consists for example of a
metal plate. Underneath this is adjoined-by an open-pore
low-compressible layer. A hygroscopic layer which can
consist of several partial layers is mounted in direct
contact with the moulding mass.
~ The invention claims~a process and the associated apparatus -
-~ 25 for manufacturing more particularly marble-like plaster
elements with high-quality visible surfaces in the most
varied configurations. For~ example single-colour or
marbled flat or relief-like plates, corner or column
elements or figurative bodies can be manufactured according
to the process according to the invention. This list makes
: -:
,,., ~. ~ : . . .
2 ~
g
no claim to being complete. The apparatus, more
particularly its elements recess, load distribution plate,
pressure elements and in particular mould base are designed
to correspond with the plaster elements which are to be
formed. The solution according to the invention allows the
low-cost manufacture of plaster elements with decorative
high-quality surface finishes. The apparatus is easy to
load with the mixture ingredients.
It i6 also simple to remove the plaster elements from the
moulds. Expensive after-treatments of the surfaces are not
required. If necessary the surface finish can be polished
~ with wax. The use of expensive surface sealing processes
~: i6 unnecessary since the plaster particles are concentrated
in the area of the finished surface and a high degree of
coalescence of the crystallised plaster particles is
produced. The finished surfaces of the plaster elements
have a higher surface strength than comparable products
known up until now. The water absorption capacity of these
~ surfaces is very low~so that the plaster elements made
i -~ 20 according to the invention can be used for a wide range of
purposes. Since the whole plaster element has a hiyh
strength, elements such as plates can be made very thin and
~ fixed by simple methods eg adhesive.
r`, ~ The invention will now be explained with reference to an
embodiment. ~The associated drawings show the apparatus in
;~ ~section during different phases of the manufacturing
process: ~
Figure 1 : Starting position with filled mould
Figure 2 : Pre-compacting of the moulding mass
Figure 3 : Compression of the moulding mass
Figure 4 : Demoulding of the moulded plaster element.
''
~ :
2~31~
-10-
- ~ ,
The apparatus comprises a lower part 3 holding the moulding
mass 5 and an upper part 2 which i5 mounted to move
vertically towards the lower part 3 when force is applied.
The upper part 2 and lower part 3 are detachably connected
together by a known spring-loaded lock 2.7 and are brought
into connection with an abutment 1, a box-like pressure
~ container.
:, .
The upper part 2 is designed aB a U-shaped recess 2.1
wherein one or more pressure elements 2.2 which are
connected to the abutment 1 are mounted at the top and one
or more pressure elements 2.3 are mounted at the bottom.
.
A pressure pipe 2.4 for the pressure element 2~3 and an air
outlet 2.5 are fitted into the recess 2.1. The pressure
elements 2.2 and 2.3 are cushions made of a flexible
material and designed to be pressure biassed by a medium.
Air or other fluids can be used as this medium. The
pressure elements 2.2 and 2.3 are connected together in
technically controlled manner.
A protruding p~rlpheral elastic seal 2.6 is fitted in the
end ~face of the recess 2.1 facing the~lower part 3 and
; connects the upper and lower parts 2,3 together in an air~
tight manner~durlng the~shaping process.~ The lower part 3
~ consists of a~ stable-shape frame 3.2 with integrated
-~ partition 3.3. The partition 3.3 consists in plan view of
' 25 two L-shaped interfitting parts. An elastic seal 3.4 is
fitted in the end face of the frame 3.2 facing the mould
base 3.1 whereby the lower part 3 is supported in air-tight
manner on the mould base 3.1. ~ The partition 3.3 adjoins
the mould base 3.1 by its sharp edges. During shaping the
partition 3.3 is held locked in the frame 3.2 by the
corresponding wedge-shaped facing side faces of the frame
~ 2~31~L
--11--
3.2 and 3.3 but during demoulding of the shaped body the
partition 3.3 is movable in the frame 3.2.
The mould base 3.1 is movably mounted on the abutment 1
wherein the side of the mould base 3.1 ~acing the moulding
mass, ie the subsequent finished surface side of the
moulded body can be smooth or structured. A load
distribution plate 4 is inserted between the upper part 2
and lower part 3 and completely covers the inner
configuration of the partition 3.3. The sandwich-like
plate has a metal plate 4.1 as the support layer beneath
-~ which is mounted a PVC perforated plate 4.2 for the
important removal of the excess air from the compacted
moulding mass 5.
One or more hygroscopic fleece layers 4.3 are provided as
the bottom layer to absorb the excess water from the
moulding mass 5.
The method of operation of the individual elements which
make up the~apparatus appears in the description of the
-~ process for manufacturing plaster elements with marble like
finished surfaces. The process will now be described in
reIatlon to the manufacture of flat stucco marble plates.
In Figure 1 the upper part 2 and lower part 3 of the
apparatus are positioned separately from;each other in the
starting position in~the abutment 1. The mould base 3.1
~X~ 25 which is mounted on runners and has the frame 3.2 on top
with the integrated partition 3.3 was loaded outside the
~; abutment 1 with a moulding mass 5 comprising a flowable
water-plaster mixture 5.1 and a superposed layer of dry
plaster powder 5.2 of even thickness. Corresponding keyed
locking means are designed to position the frame 3.2 on the
mould base 3.1. The marbled texture in the visible area of
the body to be formed can be achieved by add.ing colour
::
,. :;~ : . . .....
-12-
,
pigments to the mixture 5.1 or by previously applying
pigments mixed with plaster and water to the mould base
3.1. The moulding mass 5 is covered with a load
distribution plate 4 with a sandwich type structure. This
plate has the layered structure mentioned in detail above.
As can be seen from the drawings, the load distribution
-~ plate 4 is placed on the moulding mass 5. It is however
~; also possible for it or parts of it to be fixed on the
underside of the pressure element 2.1. The pressure
elements 2.2 and 2.3 which are coupled together by a
~`~ regulating device are impinged by pressure. Thelr pressure
impingement is attuned by the regulating device so that the
pressure element 2.3 is pressed onto the moulding mass 5 by
the load distribution plate 4 so that the air escapes
~; 15 through the air outlet 2.5 and the moulding mass becomes
compacted at the same time (Figure 2).
~.,: ~, .
As the pressure increases, the air outlet 2.5 is closed by
the pressure element 2.3, the lock 2.7 closes the upper
-~ part 2 with the lower part 3 and the moulding mass 5
becomes compressed in air-tight manner (Figure 3). During
this shaping process an air-tight closur~ is produced by
the seal 2.6 between the recess 2.1 and the frame 3.2
whereby an excess pressure, for example 0.4 MPa is formed
in the mould. ;This excess pressure is now maintained until
25~ ~the plaster particles of the flowable water-plaster mixture
5.1 have concentrated at~and near the mould base 3.1 and
the constituents of the moulding mass 5 not required for
! the setting process, such as air and excess water, are
transported towards the load distribution plate 4. At the
end of this concentration process, the pressure exerted on
ths moulding mass 5 is maintainéd to the full extent or
somewhat reduced until the shape of the plaster element is
stable so that no undesired deformation of the element can
occur. The property of the pIaster elements, that they are
~ 35 not immediately stable ln shape due to the layered
`~
:: :
i, ~ , . . .
2~3:L~l
-13-
`~:
structure of the moulding mass 5 can also be utilized to
shape the plaster elements.
The plaster element is now removed from the mould a~ shown
in Figure 4. The pressure in the pressure element 2.2 is
reduced whilst the pressure in the pressure element 2.3
remains unchanged.
This has the result that the frame 3.2 fixed by the lock
2.7 on the upper part 2 which has moved upwards is also
;~ moved upwards.
The side faces of the frame 3.2 and partition frame 3.3
facing each other in wedge formation and the movable fixing
of the partition frame 3.3 on the frame 3.2 mean that the
; plaster element moulded out of the moulding mass can be
removed from the mould without difficulty.
The stucco marble plates manufactured in this way have a
high quality surface finish. Their high abrasion
resistance, high density and-low pore volume as well as
compression strength and resistance to bending make them
comparable with natural marble.
When manufacturing angular eIements or elements with other
configurations, the recess 2.1, load distribution plate 4,
~-- pressure elements 2.2 and 2.3 and mould base 3.1 are
designed accordingly.
,
The entire manufacturing process of plaster elements with
marble-like finished surfaces can be carried out
automatically.
`
.: . : , . . -
