Note: Descriptions are shown in the official language in which they were submitted.
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A Method_ of Determilling the ~mount of Waste Veposi.te~
on F_lter_Cloths of a Drum Filter and a Device for
Carrying Out the Method
Technical Field
The invention relates to a method of determining
the amount of waste deposited on filter cloths on
the shaft of a rotatably suspended drum of a drum
filter in which soiled liquid is inside the drum whose
lower part is immersed in the filtered liquid, and
the level of the soiled liquid inside the drum is
higher than the level of the filtered liquid outside
said drum.
The invention also relates to a device for
carrying out said method comprising a drum of a drum
filter rotatably mounted on at~least two suspension-
type supporting members embracing a shaft seated on
the stationary frame of the drum filter, with soiled
liquid situated inside the drum, the lower part of
the drum immersed in the filtered liquid, and the level
of the soiled liquid inside the drum of the drum filter
higher than the level of the filtered liquid outside
said drum.
Background of the Invention
Drum filters contain a rotatably mounted drum
fitted on its circumference with filter cloths and
with two face holes out of which through one, an inlet
hole, soiled liquid, as a rule water, is led inside,
while through the other, the outlet hole, impurities
are let out, for instance by means of an off-take
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trough. The lower part of the drum filter is immersed
in the filtered liquid, and the level of soiled liquid
inside the drum of the drum filter is higher than the
level of the filtered liquid outside the drum filter.
In the heretofore known devices, the determining
of the waste amount deposited on the filter cloth
of a drum filter is carried out by deYices recording
the level heights inside and outside the drum of the
drum filter, for instance by means of float-operated
switching on and off systems, or by means of electro-
nic, pressure or optical feelers disadvantageous in
that they are apt easily to take up the waste contained
in the soiled liquid with the ensuing deterioration
of the functional accuracy.
The rotation of the drum of the drum filter
results in undulation of the liquid levels which is
another cause o incorrect working of the level height
feelers. In addition to the limited reliability of
the function, other drawbacks ~f the known devices
consist in their complicated design, high production
costs, and poor response to the changes in the level
height.
.
The drawback of the undulation of the level
recorded by means of a float has ben removed in the
US patent specification No. 3,837,216 dealing with
the measuring of the concentration of a solution float-
in8 in a liquid in a drum filter into whose container
there is fed a soiled liquid in which is mounted the 1-
drum of the drum filter, on whose circumference the
is led the filtering substance. The contaminants
gather on the outer surface of the drum whose rotation
speed is adjusted in accordance with the height of
the level in the container. Ne~t to said container and
in~erconnected with it there is provided a vertical
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column having a recording float on the liquid surface,
thus removing the faults due to the liquid undulation
in the cont~irler. The other a~ove menti.o~ Ir~wl~.~ck.~
discussed with respect to the preceding cases apply to :
this case as well. ~-
Disclosure of the Invention
The above specified drawbacks are removed by
a method of determining the amount of waste deposited
on filter cloths of the drum of a drum filter rotatab-
ly suspended on a shaft whose principle consists
in that there are recorded the changes in the total
mass (weight) of the drum of the drum filter which
correspond to the changes in the amount of waste
deposited on filter cloths and to the changes in -
the height of the level of soiled liquid inside the :.
drum of the drum filter.
The device for carrying out the method according
to the invention comprises a drum rotatably suspended
on at least two suspension-type supporting membe~s
embracing a shaft seated on the stationary frame
of the drum filter, and its principle consists in
that at least one force recorder is provided for
between the shaft and the stationary frame of the
drum filter.
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21~776
~ W094/0379~ PCT/CZ~3100019
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In a preferred embodiment, the force recorder
is sea~ed under the shaft at the place where the
shaft is embraced by the support~ng member.
The shat can be mounted on a le~er swingingly
seated on the stationar~ frame o the drum filter,
the force recorder being se~ted between the free
arm of the lever and the stationary frame of the
drum filter.
The advantage of the method according to the
invention consists in the accuracy of determining
the le~el height difference inside and outside the
drum of the drum filter and, in particular, high
reliability regardless of the amount of waste deposit--
ed on the feelers. The ad~antage of the device accor~-
ing to the in~ention consists in its simple design
due to its location outside the i~ner space of the
drum.
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Brief DescriPtion of_the_Drawin8
An e~ample of embodiment of a device for carrying
out the method according ~o the invention is schemati-
cally represented in the accompanying drawing showing
thejface of the drum of the drum filter.
Modes for Carrylng Out the Invention
Drum filters are use~ for filtering soiled
liquids, in particular water. The drum filter
comprises a drum 1 consisting in a well-known manner
of two faces with horizontal a~is interconnected
by not shown reinforcing me~bers, with not shown
filter cloths mounted along the circumference
2140776
W~94/03790 P~T/C~93/~0~19
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of the drum. The fil~er cloths are mounted in a known
manner which is not the sub~ect of this Patent Appli-
cation.
The lower part of the drum 1 of the drum filter
is immersed in the (readg-~filtered liquid. The soiled
li~uid is in a well-known manner led into the -inner
space of the drum 1 of the drum filter, and its level
height is superior to the le~el height of the (ready)-
filtered liquid. The le~el height difference provides -
for the hydrostatic pressure responsible for the
fil~ering -process going on.
The drum 1 of the drum filter is rotatably
mounted on suspension-type supporting members 2 em-
bracin~ a shaft 4, in the shown e~ample of embodiment
a roller 3 mounted on the shaft 4. In the shown e~àm-
ple of embodiment, the shaft 4 i~ rotatably seated
in the body of a single-arm leYer 5 swingingly mounted
on a stationary frame 6 of the drum filter. Between
the arm end of thè single-arm lever 5 and the
stationar~ frame 6 is situated a force recorder 7
at a d~stance from th`e fulcrum of the single-arm
le~er 5 greater than the shaft 4. In the shown example
of embodiment, the suspension-type supporting members
2 are two in number and they embrace the circumference
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of the drum 1 of the drum filter. However, the number
of the suspension-type supporting member~ can be
more than two. The terminal (outward) suspension-
t~pe members 2 can embrace well-known not represented
supporting rings fixed to the faces of the drum 1
of the drum filter. At least one of the suspension-
type ~upporting members 2 is coupled with a not shown
well-known driving device controlled by a not shown
well-known control unit which is by means of a not
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shown line connected with the force recorder 7.
In another embodiment, the single-arm le~er
5 can be replaced b~ a double-arm lever.
On the stationary frame 6 of the drum filter
is rotatably mounted a stabilizing roller 8 touching
the circumference of the drum 1 of the drum filter
and stabilizing its position during the rotation
of the drum l, in particular in its initial and final
phases of rotation, i.e., in the s~art and stop-motiQn
phases in which impacts occur. More than one piece
of the stsbilizing roiler 8 can be used.
The suspens~on-type supporting members 2 can
embraee the shaft 4 directly, with no rollers 3 inter-
po:8ed ~betweèn them, and the force recorders 7 may
h~: ba in other embodiments located~between the shaft
4 and the stationary frame 6 of the drum filter,
at leas~ one force recorder 7 of any known type being
obligatory for each drum 1. ~lso, the shaft 4 can
be suspended on the force recorder 7 at due place.
In :the shown e~ample of embodiment, the shaft
~: 4 is made as a through shaft throughout the length
, , o~i the drum 1. However, it can also be made as a
diYided shaft seated in a well-known way on the stati-
: onary frame 6 of the drum 1 of the drum filtèr.
Soiled liquid led into the inner space of the
drum 1 of the drum f~lter passes during the filtering
proce~s through the filtering cloths arran8ed on
the circumference of the drum 1 and on which deposits
the waste while the (ready-)filtered liquid is col-
lected in the space outside the drum 1 and is in
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W094/03790 2 1 4 0 7 7 6 PCT/C~93/00019
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a well-known manner led away from there. The
hydrostatic pressure due to ~he level height
difference inside and outside the drum 1 keeps the
filtering process going on. The waste continuously
depositing on the filter cloths impairs their permea-
bility for the liquid, and the leYel inside the drum
1 rises. When the amount of the waste deposi~ed on
the filter ~loths is excessive, it is necessary to
turn the drum 1 a bit; at this, a large part of the
waste falls into a well-known waste off-take trough
which is in a well-known manner located in the upper
part of the inner space of the drum 1 of the drum
filter. After the turning movement of the drum, into
the filtering process enter the non-deposited filter
cloths, and the filtering process goes on with the
original or only slightly decreased intensity.
The turning moYement is imparted to the drum
1 by a command given by a well-known not shown control
unit to a well-known not shown driYe de~ice. The
control unit receives signals coming from the force
recorder 7 recording the mass (weight) of the drum
1 of the drum filter. The changes in the mass of
the drum 1 of the drum filter due both to the deposi-
tion of the filter cloths and to the rising level
of the soiled liquid inside the drum 1 of the drum
ilter are ev~luated by the control unit which gives
out a signal for turning the drum 1 when preset vslues
ha~e been reached. In the same manner is watched
also the ma~imum level of so~led liquid in the drum
1 of the drum filter corresponding to the complete
obstruction of filter cloths of the drum 1 of the
drum filter, and at which ~he control unit sends
out a signal for pu~ting the drum filter out of opera-
tion and for e~changing the filter cloths.
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The monitoring of the increase in the total
mass of the drum 1 of the drum ilter permits to
check the changes in the amount of waste deposited -~
on the filter cloths of the drum 1 and thus to control .
the sction of the drum filter.
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