Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a process of
' producing fiber boards, in particular asbestos-cement plates,
: wherein a felt band loaded with the fiber layer is led between
a format roll and a breast roll, and wherein the loading of the
felt band with the fiber layer is carried out by deposition onto
, the felt band and by suction from its opposite side.
, A known process of this art applies one single tank
for the deposition with a vacuum head serving for the suction of
- the fiber layer to the felt band.
, 10 It is a disadvantage of the known process that,
,' because of using one single vacuum head, the fiber layer is not
drained (dewatered) sufficiently and that the fiber layer cannot
, be produced with a sufficiently uniform thickness.
,- In another known process, the loading of the felt
' band with the fiber layer is carried out by means of a filter
cylinder rotating in a filter cylinder tank filled up with a
mixture of asbestos cement and water, rather than by deposition
from the pulp.
, It is a disadvantage of this process that the filter
~, 20 cylinder can absorb only relatively low fiber concentrations and
- that the mixture of asbestos-cement and water (asbestos-cement
pulp) must be of relatively high fluidity. For this reason, it
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`,', is pos,sible for the fibers in the asbestos-cement pulp to be
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j',, oriented in the transport direction while they are absorbed by the
,' filter cylinder. Thus, asbestos-cement plates or asbestos-cement
' products are produced which have various strengths in various
,,, directions. Among other things, the relatively high fluidity in
,," the known process results from the fact that the drying arc of
' the filter cylinder is relatively small.
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~`, 30 A further disadvantage of this known process results
" from the fact that the highly fluid asbestos-cement pulp is
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inclined to precipitation, so that a settling out should be
prevented by applying reels in the filter cylinder tank. The
ree~ls should have relatively high rotation speed and they generate,
therefore, turbulences in the filter cylinder tank.
Disadvantageously, these turbulences lead to a non-
uniform thickness of the layer absorbed by the filter cylinder,
which results in a non-uniform strength and/or density of the
plates produced in this manner.
The non-uniformity of the plates produced also
e~tends to their structure since flakes are formed in the
asbestos-cement pulp due to the turbulences generated by the reels.
Therefore, the scope and aim of the present invention
is to provide a process which makes it possible to efficiently
produce fiber layers with uniform thickness.
In accordance with the invention, two processes
are provided for solving the stated task.
First, the task according to the invention is solved
by condensing and dewatering the fiber layer, after depositing
it from the pulp onto the felt band, in a set-up consisting of a
~ 20 filter cylinder and a couch roll associated with it.
; As a result, during passing through this set-up, `
, ..
first, a good dewatering and, second, the required pre-condensing
will be obtained. Besides this, from the passing through between
the cylinders pressed to each other, a uniform plate thickness
:
- results during the dewatering and pre-condensing process, whereby
it is also possible to adjust the plate thickness by altering the
distance between the cylinders and simultaneously altering the
; vacuum in the deposition process.
- Furthermore, for the solution of the same task,
.- .
the invention provides for the possibility that various amplitudes
of vacuum be applied to the loaded length of the felt band in the
c1eposition process.
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In this manner it becomes possible to produce
fiber boards of uniform thickness and to accomplish their
efficient dewatering, first, by depositing the fibers over wide
portions of the felt band under a vacuum and, second, hy adjust-
ing this latter. It is, e.g., possible to increase the vacuum
in the transport direction in accordance with the increasing
thickness of the fiber layer either continuously or as a function
of the asbestos-cement pulp composition in definite proportions,
thereby producing a uniform thickness over the loaded length of
the felt band.
As compared with the known processes, both processes
have the advantage that with their use such fiber products, in
particular asbestos-cement plates, are produced which are extremely
; uniform in their structure, strength, and density.
Another advantage of the processes according to the
:
invention consists of the fact that the asbestos-cement pulp may
be of relatively low fluidity because the loading of the felt
, band with the fiber layer in the suction process is promoted by an
additional force namely by the vacuum acting fro~ outside. On
the contrary, in the process wherein the loading is carried out by
means of a filter cylinder, the fibers are deposited only by
hydrostatic pressure, pre-determined by the dimensions of the
filter cylinder tank, which is relatively low. In this way, all
disadvantages resulting from the high fluidity of the asbestos-
:f '
cement pulp are prevented by the process according to the
; invention.
' Furthermore, in the processes according to the
; invention the fiber layer from the asbestos-cement pulp is
absorbed by the felt band in a disordered state corresponding to
30 the momentary positions of the fibers. Although an orientation of
the fibers, similar to that in the known processes, also takes
place in the processes according to the invention, it does so to
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a much lesser extent since the fibers attached by suction are in ~ -
~essence fixed on the feltband in their state of deposition in a
; more or less irreversible manner and they are transported away in
this state.
Finally, contrarily to the known processes, the
process according to the invention has the advantage of lesser
waste material, i.e., only a small amount of solid material goes
over into the filtrate water.
Finally, as compared with the processes mentioned
in the introduction, the processes according to the invention
insures a considerable increase in productivity.
; Both processes according to the invention can be
combined in a particularly efficient manner, i.e., in addition to
the described variable loading under vacuum, the dewatering and
condensing may also be carried out by means of a set-up consisting
of a filter cylinder and a couch roll.
; To insure a uniform thickness over the entire width
of the fiber plate being produced, it is of particular advantage,
wh`en thé loading of the fibers in the deposition process is carried
out, to be able to vary the vacuum over the width of the felt band
; being loaded.
In this manner, it is possible to adjust the vacuum
within a variable range over the width of the felt band so that a
",
~J uniform thickness of the produced plates may be insured over the
width of the plate depending on the composition of the asbestos-
cement pulp, rate of production, fiber length, and the filtration
resistance of the felt band.
When implementing the process according to the
invention, in an equipment comprising a deposition tank for loading
the fiber layer on one side of the felt band and a vacuum tank on
; its other side, it is of advantage to attach to the deposition
tank a set-up which consists of a filter cylinder and a couch roll
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for condensing and dewatering, and for producing plates of uniforrn
thickness.
In place of the set-up co~nsisting of a filter
cylinder and couch roll, the deposition tank itself can be
replaced by such a series of deposition tanks, extending over the
loaded length of the felt band, whose individual tanks carry out
the loading under various vacuums.
In a particularly efficient manner, it is also
possible to use this set-up, consisting of a filter cylinder and
a couch roll, together with the series of deposition vacuum tanks.
In addition to the advantages resulting from the
process itself, this equipment has the further advantage that,
contrarily to the known equipment operating by loading a filter
cylinder with the fiber layer - it is less sensitive to dirt. The
known equipment should, as a rule, be stopped for at least one hour
in every twenty-four hours for cleaning the filter cylinder. No
such stoppages are needed for the equipment according to the
invention. Finally, the equipment according to the invention can
be constructed with much smaller dimensions than those of the known
equipment and its production costs are, therefore, less.
By applying independent loading to the individual
tanks in the vacuum tank series, it is possible to increase the
vacuum in the transport direction according to the increasing
- thickness of the fiber layer either continuously or as a function
of the type and composition of the asbestos-cement pulp in definite
proportions in the deposition tank.
On the other hand, it might be necessary to apply a
higher vacuum to the vacuum tank which is first in the transport
direction than to that which is last when such a current should
be generated (in a manner described below) in the deposition tank
which is stronger in the region of the first vacuum tank than it is
in the region of the last one.
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It is of particular advantage to divide the
individual tanks in the vacuum tank series over the width of
thle felt band into further individual tanks acted upon by a
vacuum independently from each other. In this manner, the vacuum
is made, within a practically unlimited range, adjustable
simultaneously both over the width and over the loaded length
of the felt band and the ~equirements can be met under any
practically occurring conditions.
It is of advantage to arrange the deposition tank
, .. ~ .
and the series of vacuum tanks in such a manner that the felt
band pass through the equipment in an approximately vertical
direction from below up. In this manner, there will be no --
sealing problems at the upper end of the deposition tanks and
vacuum tank series, respectively. Besides, this arrangement
insures a considerable saving in space.
On the other hand, the equipment according to
the invention makes it possible to arrange the deposition tank
and the vacuum tank series in such a manner that the felt band
is at an angle to thé horizon~al and that it passes through the
equipment upwardly.
Depending on the material being used, consistency
present in the deposition tank, type and shape of the vacuum
- tanks, and the vacuum applied, one can always choose the
optimum slope for the set-up consisting of the deposition tank
and vacuum tank series. The set-up may be realized in such a
manner that, in case of need, even a subsequent re-adjustment
is possible during operation.
For this aim, it is convenient to arrange both the
deposition tank and the vacuum tank series in the same frame
whose vertical columns are parallel to each other and whose
lower ends are hinge connections with the fixed points while
their upper ends are connected by means of a traverse so that a
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1047293
four-bar linkage is formed. For adjusting the required slope,
the columns along with the vacuum tank series and the deposition
tank, are tilted whereby the columns are movable like the sides
of a parallelogram. The columns are fixed in the adjusted position.
At least one guide pulley of the felt band is
installed at the lower end of the set-up consisting of the
deposition tank and vacuum tank series. In this manner, the
pre-stressing of the felt band is, at least at small slopes,
not substantially changed and so small slopes may be set up
without any change in the construction. In case of larger slopes,
the corresponding guide pulleys should be adjusted or shifted
" simultaneously while adjusting the slope of the frame to maintain
the prestressing of the felt band. For this purpose, at least
one more felt band pulley, adjustable in the vertical direction,
is provided either on the internal or on the external side of one
of the columns.
According to the invention, the equipment makes
possible the exchange of the deposition tank in a few manual
operations in order to produce bands of various widths. Here
the equipment according to the invention has an advantage, as
. .
; compared with the known equipment operating with a single filter
tank in which the exchange of the filter cylinder is expensive
and troublesome, that in an advantageous manner, the deposition
tank is positioned on, and detachably united with, the brackets
.. ~ .
~ fixed on the frame.
,: ,
The disordered state of the fibers on the felt band
and the attachment of the fibers in their momentary position,
which are aimed at, are obtained in an efficient manner when such
" .,; .
a rate of flow and/or direc-tion of flow are imparted to the
asbestos-cement pulp in the deposition tank that correspond with
~, those of the felt band in the region of the deposition tank.
Several possibiliiies are given to insure such a flow rate: e.g.,
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~047293
the required flow rate can be obtained by using at least one
centrifugal pump.
of particular advantage is the case wherein a
diaphragm, forming a stream channel with the felt band, is
installed face to face and substantially parallel with the felt
band in the deposition tank. The diaphragm is adjustable in
the cross-direction of the longitudinal axis of the felt band
and/or in its angular position with respect to the felt band in
order to conform the channel cross-section to the existing
conditions. It is advantageous to provide the lower ehd of the
diaphragm with a bent edge to promote the inflow. In an
advantageous manner, the diaphragm may, finally, be formed as a
flexible membrane in order to equalize the pressure fluctuations
and, possibly, a non-uniform or pulsating stream.
The stream is produced by the diaphragm in the
channel between itself and the felt band due to the fact that, -
because of transporting away a portion of water sucked in the
channel into the vacuum tanks, a lesser amount of total asbestos-
cement material will be transported upward and, therefore, the
level of liquid in the channel will be lower than that in the
main chamber. For this reason, a pressure difference is created
between the channel on the side of the felt band and the main
chamber, which results in a stream of asbestos-cement pulp into
. ~
the channel.
The stream or its velocity can be affected or
controlled by adjusting both the distance and the angle of the
... .
~- diaphragm as described above.
. .
Finally, in a known manner, reels may be installed
in the deposition tank to prevent a settling out. The rotation
velocity of these reels may, however, be lower than that in the
known equipments.
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In the transport direction, additional dry
vacuum tanks can be advantageously attached to the set-up con-
sisting of the deposition tank and vacuum tank series.
To insure an improved dewatering and a simultaneous
condensing, the attachment of a set-up consisting of a filter
cylinder and a coach roll paired with it is provided to the dry
vacuum tank. Here, it may be of advantage when the couch roll,
too, is designed as a suction roll acted upon by a vacuum. The
action of vacuum has the aim to promote the easier detachment of
the fiber layer from the filter cylinder, to which it has been
pressed so that the fiber layer will stay attached to the felt
band.
The filter cylinder and the couch roll are
advantageously located in the same frame as the deposition tank
and the vacuum tank series, and are adjustable together with
them.
A washing apparatus for the felt band can be
attached before the deposition tank and vacuum tank series. The
said washing apparatus consists of a washing vacuum tank, an acid
- 20 basin, another washing vacuum tank, and a dry vacuum tank.
For obtaining greater layer thicknesses and/or
condensing, as well as dewatering, several set-ups composed of
; deposition tanks and vacuum tank series, as well as filter
cylinder and a couch roll-can be attached one after the other.
;~,
In this regard, it is efficient when a sub-conveyor is applied
inside every such set-up. This subconveyor takes up the fiber
layer and, transports it to the felt band passing through only
the set-up between the filter cylinder and the couch roll: this
makes it superfluous that the felt band already loaded with a
fiber layer should pass through another set-up which would lead
to difficulties.
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It is of advantage to provide the sub-conveyor in
every individual set-up with a washing apparatus composed of a
washing suction apparatus, an acid basin, and a dry vacuum tank.
The apparatus according to the invention may also
~e used for producing other fiber- and asbestos-cement products
such as pipes or plates having longitudinally directed structures
on them. Besides, the apparatus according to the invention may
be used for dewatering and dehydrating of other pulp and sedi-
mentary-type substances, e.g., in filter plants with the aim of
re-using the precipitation products.
According to a broad aspect of the present invention,
there is provided a method for producing fibre-boards, and more
particularly asbestos-cement boards, wherein a felt strip to
which a fibre mat is applied is fed to a shaping roll and a
breast roll. The fibre mat is applied to the felt strip by
floating it thereonto and applying suction to the other side
thereof. The method is characterized in that the suction is
applied, during the floating process, over a relevant length
of the felt strip and at a different negative pressure. The
method is further characterized in that flow velocity and direc-
tion is imparted to an asbestos-cement slurry in a float-box.
The velocity and direction imparted to the slurry corresponds to
that of the felt strip in the vicinity of the float-box. Fur-
ther, the method is characterized in that the fibre mat which is
floated onto the felt strip is compacted and drained, after the
floating process, by means of an arrangement comprising a screen
cylinder and a couching roll.
,.
, According to a further broad aspect of the present
invention, there is provided an apparat~s for producing fibre-
boards, and more particularly asbestos-cement boards, wherein
a felt strip to which a fibre mat is applied is fed to a shaping
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104'7293
roll and a breast roll, with the fibre mat being applied to the
- felt strip by floating it thereonto and applying suction to the
other side thereof. The apparatus comprises a float-box for
treating one side of a felt strip with a fibre-bonding-agent mat.
A suction device is applied to the other side of the felt strip
and consists of a row of suction boxes separated from each other
and arranged one behind the other in the direction of travel of
the felt strip. Each of the suction boxes has a negative pres-
sure applied independently thereto. A screen cylinder and a
couching roll are positioned after the float-box.
The invention will be better understood by an
examination of the following disclosure together with the
accompanying drawings, in which:
FIGURE 1 is a schematic diagram of one embodiment
of the equipment according to the
; lnvention;
FIGURE 2 is a schematic diagram of another
embodiment; and
FIGURE 3 shows the design of an embodiment similar
to Figure 1.
Figure 1 illustrates a format roll 1 and a breast
roll 2~ of which one or both may be driven rolls. Transport band
27 transports away fiber layer 5. This layer is led to format
`- roll 1 and breast roll 2 by means of felt band 3, which is guided
by several guiding pulleys and goes around and passes between the
format roll and breast roll.
The loading of felt band 3 with fiber layer 5 is
carried out in deposition tank 6, positioned on one side of the
felt band, in which reels 7 are installed. On the other side of
the felt band, a series of vacuum tanks 8, consisting of individual
vacuum tanks 9 are located which may be acted upon by a vacuum
independently from each other, in order to produce a fiber layer of
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~0~7293
uniform thickness over the width of the felt band, in the trans-
port direction.
- In Figure 1, deposition tank 6 and vacuum tankseries 8 are arranged in such a manner that felt band 3 passes
through the set-up vertically from below up. However, this set-up
can be tilted so that it is at an angle to the horizontal
in a manner described below.
In deposition tank 6, face to face and sub-
stantially parallel felt band 3, diaphragm 10 is installed. The
diaphragm forms a stream channel 11 with feIt band 3. Diaphragm
10 is adjustable in the direction across the longitudinal axis of -
the felt band and/or in its angular position with respect to felt
band 3 in the direction of arrow 12. The lower end of the
diaphragm is provided with bent edge 13. The said diaphragm may
also be designed as a flexible membrane.
.
The equipment described operates as follows:
; In channel 11, a stream is generated by diaphragm
10, while a portion of water is transported away by vacuum tanks
9, so that less total material is transported upward from the
asbestos-cement pulp and a lower liquid level 14 is set-up in
channel 11. The liquid level in maïn chamber 15, given as an
' example, is designated with a dotted line and number 16. As a
consequence, a pressure difference is created between channel 11
. . :
~ and main chamber 15 and, therefore, an upward streaming of the
7 ' asbestos-cement pulp is generated in channel 11. In this manner,
:,
a velocity of flow may be set up which, at least in its direction,
conforms to the transport rate of felt band 3. This makes it
; possible to fix the momentary disordered state of all streaming
"~ fibers by means of vacuum tanks 9 and to eliminate all dis-
:
'~ 30 advantages o the known process, resulting from a disadvantageous
setting out of the fibersO
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10472~3
Additional dry vacuum tanks 17 are subsequently
attached to deposition tank 6 and vacuum tank series 8.
In order to obtain an improved dewatering and a
sirnultaneous condensing, a set-up consisting of filter cylinder
18 and couch roll 19 is subsequently attached to dry vacuum tank 17.
In the illustrated example, couch roll 19 is also designed,as a
suction roll, being under the action of a vacuum, in order to
promote the separation of the condensed fiber layer from filter
cylinder 18 by the felt band.
To wash felt band 3, an apparatus composed of wash-
ing vacuum tank 22, acid basin 24, another washing vacuum 23, and
a dry vacuum tank 26 is installed before deposition tank 6 and
vacuum tank series 8.
;
Figure 2 shows an embodiment similar to that in
., ~
' Figure 1. Here, there are several set-ups consisting of
deposition tank 6 with vacuum tank series 8, as well as filter
' cylinder 18 and couch roll 19 attached one after the other to
.~ .
~ obtain, first, greater layer thickness and, second, improved
.,~
'~ condensing.
, 20 In this example, felt band 3 does not pass throughthe set-up consisting of deposition tank 6 and vacuum tank series
, 8, but it is loaded by means of sub-conveyor 28, guided by guide;~ pulley 29~ which passes'through this set-up. This conveyor takesup fiber layer 5 from deposition tank 6 and delivers it to felt
band 3 in the region between filter cylinder 18 and couch roll 1~.
Sub-conveyor 29 runs in the direction of arrow 30: the felt band,
';~; in the direction of arrow 31.
Each individual set-up is provided with a washing
, apparatus 32 for sub-conveyor 29. This washing apparatus, in the; 30 same way as washing apparatus 22, consists of washing vacuum tank
23, acid basin 24, another washing vacuum tank 25, and a vacuum
tank 26.
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In the embodiment according to Figure 2, the felt
band is not driven by the format-or breat roll, but has a
; separate drive 33 with driven main roll 34 and press roll 35.
Figure 3 is an illustration of practical equipment
according to the schematics of Figure 1 and Figure 2. As seen in
; Figure 3, deposition tank 6 and vacuum tank `series 8 with individual
vacuum tank 9 are arranged in frame 36 whose vertical columns 37
are parallel to each other and their lower ends have hin~e
connections with the fixed frame points 38 while their upper ends,
~ 10 via link point 39, are connected by means of traverse 40 so that
a four-bar linkage is formed. This makes it possible to move
columns 37, like the sides of a parallelogram, in the direction
of arrow 41 and to set up the slope for deposition tank 6 and
vacuum tank series 8. The columns are fixed in the adjusted
position.
~ s also seen in Figure 3, deposition tank 6, along
with vacuum tank series 8, is positioned on, and detachably
united with, brackets 43, 44 fixed on columns 37 of frame 36 so
that the deposition tank may readily be exchanged either
~,~ 20 separately or together with vacuum tank series 8.
, ~ . .
`, In the illustrated example, a set-up consisting
of filter cylinder 18 and couch roll 19 is also positioned on
~'- traverse 45 connected with frame 36. This traverse 45 has a
hinge connection with column 37 in the case so that its slope is
, adjustable.
Dewatering apparatus 21 can also be supported by
the frame. When additional columns 46 are required, these are
`; connected at their upper and lower ends by means of hinge points
with traverse 49 supporting dewatering apparatus 21.
,~ 30 In order to make possible the set up of small
,' changes in the slope without additional adjustments, at least one
,, .
of the guide pulleys 4a is arranged close to link point 38 at the
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lower end of deposition tank 6 or of vacuum tank series 8. When
larger slopes are needed, the adjustment of at least one more guide
pulley 4b is required. Guide pulley 4b is adjustable in height
in the direction of arrow 42 on the corresponding column 37. The
othér pulleys, such as pulley 4c above filter cylinder 18, may
also be adjustable and they may be fastened in their position of
adjustment. Finally, it is also possible to connect the dis-
placement of the guide pulley with the tilting motion of fr~me 37
by means of a transmitting medium.
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