Note: Descriptions are shown in the official language in which they were submitted.
~ he invention relates to a metering device and, more particularly,
to such a device for metered addition of a liquid additive, such as a cross-
linking agent, for example, in liquid form to the base material or main
component of synthetically insulated cable.
In such a heretofore known device (German Published Non-Prosecuted
Application DE-OS 26 01 249) the addition of liquid peroxide is effected
directly into an extruder in dependence upon the respective base material used
for producing especially cross-linked polyethylene-insulated high-voltage cable.
For this purpose a metering device is connected in advance or upstream of an
extruder continuously producing the synthetic material-;nsulation, and the
liquid peroxide required for the cross-linking, for example, of the poly-
ethylene, is initially fed by a transfer pump to a storage vessel which is
maintained at a uniformly low temperature.
A metering pump is connected behind or downstream from the storage
vessel which advances or transfers the peroxide through a measuring device for
the throughput or flow rate, an electric safety valve with a rotation measuring
device and another electrovalve to the point of injection into the extruder.
With such a heretofore known construction, the storage vessel, the
metering pumps, the measuring devices as well as the electrovalves are
serially connected so that during a breakdown and/or disturbance of only one of
these essential aggregate units forming the metering device of the prior art,
the orderly flow of the peroxide is impaired in a disadvantageous manner and
thereby endangers trouble-free cross-linking of the base material or main
component in the extruder.
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It :Ls accordingly an object of the invention to provide a metering
device which avoids the disadvantages of the heretofore known metering devices
of this general type and which, more specifically, assures the orderly continuous
charging or feeding of the extruder with liquid cross-llnking medium also at
least after one of the essential aggregate units forming the metering device has
already become impaired due to a disturbance or the like.
With the foregoing and other objects in view, there is provided, in
accordance with the invention, a device for metering a liquid additive compris-
ing two parallel storage vessels, means including parallel stop cocks and
parallel magnetic shut-off valves, respectively, for connectlng the storage
vessels to one another, two parallel purification filters, means including a
magnetic change-over valve and a plurality of drain cocks connected in parallel
therewith, in turn, connecting the storage vessels to the purification filters,
the drain cocks being located downstream from the magnetic change over valve
in flow direction of liquid additive therethrough, a pulsation damper having an
inlet end and an outlet end, two distributor cocks mutually connected by a by-
pass line and connected in parallel arrangement with a liquid flow meter, puri-
fication filters being connected through the parallel arrangement to the inlet
end of the pulsation damper, a compensating vessel~ means including a magnetic
inlet valve connecting the compensating vessel to the outlet end of the pulsa-
tion damper, and a parallel assembly of similar metering pumps cooperatively
connected through an outlet li~e to an extruder and being also connected to the
inlet end of the pulsation damper.
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In this manner, upon the occurrence of a fault within the device,
substitute paths can be created which, by by-passing the one or more faulty
units, assure a further orderly continuous flow of the cross-linking medium to
the extruder, so that the operation of the extruder suffers no impairment.
To avoid a pulsation of the transfer flow which would become notice-
able in the liquid flow meter and would make an exact measurement lmpossible,
the pulsation damper is located, in accordance with another feature of the
invention, at the same height level as ~hat of the storage vessels and extends
over the entire height thereof.
So as ~o be able to actuate the magnetic valves and the like auto-
matically in dependence upon the liquid level in the storage vessel~ and
according to a further feature of the invention, a sensor, respectively, is
disposed in each of the storage vessels.
In accordance with an added feature of the invention, the sensor has
a maximal contact and a minimal contact.
In accordance with an additional feature of the invention, liquid~
level indicating means are included, and the maximal contacts of the respective
sensors are connected galvanically to the magnetic shut-off valves, the transfer
pump and the liquid-level indicating means.
In accordance ~llth yet another feature of the inven~ionJ the
~,etering device include.s liquid-level indicating means~ and the
mini~al contacts of the respective sensors are galvanical'ly con-
nected to the~ magneti.c shut-of~ valves~ ~he trans~er~ pu~5 the
llquid-level indic~tin~ means~ the magnet1c inlet valve and. the
magnetic change~over valve~ ' , ..................................... ..
In accordance with yet a ~urther feature of the ~nvention, ~the
magnetic change-over valve is connected to the storage vesse1s.down-
stream therefrom in direction'of ~ravel of a liquid therefrom5 one
of the draln cocks being serially connected with the magne~ic
change-over valve.
In accordance with yet an added feature of the invention5 the,one~ .'
of the drain cocks is manually actuatable, and t~o others o~ the
drain cocks are also manua].ly actuatable and connected in.p~rallel.
with ~he one of the draln cocksv ~ , , '
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In accordance with yet an additlonal feature o~ the invention, all
three of the drain cocl~s are cooperatively connected to a ~ilter
inlet cock. : '
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In accordance with an additional feature of the inventlon~ the
metering device includes a filter outlet cock~ both the filter
inlek anci the ~ilter outlet cocks being constructed as ~anually
ac~uatable t~ree-way cocks~ and t~Jo purification ~ilters con-
nected in parallel between the filter inlet cock and the filter
outlet cock.
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In accordance with a further feature of the invention, the device
includes two distributor cocks mutually connec~ed by a by-pass line and
connected to the filter outlet cock downstream therefrom.
For the purpose of monitoring, in accordance with an added feature
of the invention, a liquid flow meter providing an exact measurement value of
the liquid flow is received in a housing, the liquid flow meter being co}mected
in parallel with the by-pass line; the housing serves as protection against
explosion.
In accordance with an addi-tlonal feature oE the invention~ one of
the distributor cocks has an inlet connected directly to the filter outlet cock,
and the other of the distributor cocks has an outlet connected to a pulsation
damper.
In accordance with the feature of the invention wherein the pulsation
damper is connected through a magnetic inlet valve to the compensation vessel,
a very rapid level balance is thereby effected in the pulsation damper at the
instant of change-over from one to the other storage vessel.
In accordance with another feature of the invention, two metering
pumps are connected in parallel with the pulsation damper, and two manually
actuatable pump cocks associated with each oE the metering pumps; only one of
the metering pumps being in operation while the other stands ready in case of
a disruption. By closing the respective pump cock, the metering pump which is
not operating can be removed for servicing and/or repair purposes.
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In accordance with a further feature oE the invention, an extruder
and an outlet line connected to the extruder are pro~ided, both of the metering
pumps being connected in common with the outlet line; thereby assuring continu-
ous flow of the cross-linking medium.
In accordance with an added feature of the in~ention, the metering
device includes two distributor cocks mutually connected by a by-pass line and
connected to the filter outlet cock downstream therefrom, a liquid flow meter
received in a housing and connected in parallel with the by-pass line, and a
sensor, respectively, disposed in each of the storage vessels, the storage
vessels, the sensors, the magnetic change-over valve, the three drain cocks,
the fllter inlet cock, the purification filters, the filter outlet cock, the
distributor cocks, the liquid flow meter, the by-pass line, the housing for the
flow meter, and the pulsating damper being all received in an equipment housing.
In accordance with an additional feature of the invention, a poten-
tiometer is operatively associated with the metering pumps for regulating rotary
speed thereof.
In accordance with yet another feature of the invention, the device
includes an extruder with a worm connected to the metering pump, and the
potentiometer is also operatively associated with the extruder worm so that the
rotary speed of the metering pumps regulated
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thereby is dependent upon the rotary speed o~ the extruder worm.
In accordance ~lith yet a further feature o~ the invention5 the
metering device includes an indicator device connected to at lea~t
any one of the liquid ~low meter5 the potenciometer and the extrude~
worm.
In accordance with yet an added feature o~ the invention~ the
indicator device has tolerance indicia thereon, the magne~ic change-
over valve being actuatable in response to an indicator valve ex-
ceeding one of the tolerance indicia ~or changlng over ~rom the
~hen operating metering pump to the other metering pump.
In accordance wlth yet an additional feature of ~he invention, the
metering device includes a calibratlng potentiometer operatively
associated with the indicator devlce for shi~tin~ the zero point
there or . . -
In accordance with another feature o.- the invention~ the metering
device includes sensor means within the equlpment housing for
monitoring a concentration of additive vapor within ~he .equipment .
housing.
In accordance ~1ith a concomitant ~eature Or the invention~ the
metering de~ice includes sensor means outside the equlpment
housing ror monitoring a concentration o~ additive vapor outside
the equ.ipment housing
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Other features which are considered as characteristic for the in-
vention are set forth in the appended claims.
Although the invent1on is illustrated and described herein as em~
bodied in meterin~a device, it i8 nevertheless ~ot intende~ to be
limited to the details shown5 since variou.~ modifl~atLons and
structural changes ~ay be ~ade therein without departirlg from th~
spirit of the inven~ion and within the scope and range of equiva-
~lents of the claims.
The construction and me~hod of operation of the invention,
however, together wLth.additional objects and advantages thereo~
will be besk understood from the followina description fspeci~ic
embodiments when read in connection with the accompanying drawings~
in which:
FIG. 1 is a diagrammatic view of the metering device according to the
invention; and -
~IG. 2 is a clrcuit diagram thereof.
.
Referring now to the fi-gures of the drawing~ thera is shown therein . ..
a transfer pump 1 which is connected at one side thereof through.a
suitable line 2 to a supply vessel 3 for liquid peroxide or the llke
and, at the other side thereof, through a line 4 to a dirt f~lter 5.
The dirt filter 5 is connected through a trans~er llne 6 to a compen- -
sating or equalizing vessel 7. Two manually actuatable shutoff..
valves or stopcocks 8 and 10 as wel} as two magnetLc shutoff valves 9
and 11 additionally lead t.o the transfer line 6. In flow direction
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from the pump l, the stopcock 8 and the magnetic shutoff valve 9 disposed
parallel thereto are located upstream of a storage vessel 12 and connected
thereto, ~hile the stopcock lO and the magnetic shutoff valve 11 disposed
parallel thereto are located upstream of a further storage vessel 13 and con-
nected thereto.
A probe or detector 14 having a maximal contact 14a and a minimal
contact 14b is disposed in the storage vessel 12, and another probe or detector
lS with a further maximal contact lSa and a further minimal contact 15b is
provided in the other storage vessel 13. The contacts 14a, l~b, 15a, 15b, as
shown in Figure 2, are galvanically connected to the magnetic shutoff valves 9
and 11, respectively, the transfer pump 1 as wel.l as a level indicator 16. The
minimal contacts 14b, 15b open the magnetic shutoff valves 9 and 11, respective-
ly, and a magnetic inlet valve 17 associated with the compensating or equalizing
vessel 7 and closable by a non-illustrated conventional timing element. The
minimal contacts 14b, 15b also start the transfer pump 1 up and signal a lack
or deficiency of material in the level indicator 16. In addition, the minimal
contacts 14b and 15b actuate a magnetic change-over valve 18 disposed in
unidentified discharge lines of the ~torage vessels 12 and 13. The maximal con-
tacts 14a and 1.5a close the magnetic shutoff valves 9 and 11, respectively,
shut off the transfer pump 1 and extinguish the material-deficiency signal to
the level indicator 16.
A manually actuatable discharge valve or drain cock 19 is connected
to the magnetic change-over valve 18 directly, downstream therefrom. Two
additional manually actuatable drain cocks 20 and 21 are provided in parallel
with the first-mentioned drain cock 19, the additional drain cock 20 being
directly connected to the storage vessel 12, and the other additional drain
cok 21 being directl.y colmected to the storage vessel 13.
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These three drain cocks 19, 20 and 21 work together upon a Eilter
inlet cock 22 constructed as a manually actuatable three-way cock or valve.
Two parallel-connected purifying filters 23 and 24 are connected, on the one
hand, to the filter inlet cock 22 and terminate together, on the other hand,
in a filter drain cock 25. This filter drain coc~ 25 is a manually actuatable
three-way cock. A distributor cock 26 located downstream from and connected to
the filter drain cock 25 i5 likewise a manually actuatable three-way cock, and
yet another distributor cock 27 is connected to the distributor cock 26 down-
stream therefrom. Between the two distributor cocks 26 and 27, a liquid flow-
meter 28 as well as a bypass line 28a, in parallel therewith, is connected~
This liquid flowmeter 28 is disposed in a housing 29 ventilated by a non-
illustrated external forced-air source. The additional distributor cock 27 has
an outlet connected to a pulsation damper 30.
The components 12 to 15 and 18 to 30 of the monitoring device accor-
ding to the invention are disposed in a closed and non-ventilated equipment
housing 31. The inner space of the equipment housing 31 is kept at a suitable,
constant temperature level in order to eliminate temperature-dependent viscosity
deviations. Variations in the temperature are made known by a non-illustrated
suitable temperature indicating device. Furthermore, the magnetic change-over
valve 18 is made explosion-proof, and the liquid flow meter 28 is installed in
the forced-ventilated housing 29. This housing 29 has an inspection or
monitoring device 32 which permits commencement of the operation of the metering
device according to the invention only if a safeguard against explosion is
Qssured, or shuts off the liquid flow meter 28 only if a fault or failure occurs
ln the safeguard against explosion.
The pulsation damper 30 which is disposed at the same level as that
of the storage vess~ls 12 and 13, is connected through the magnetic lnlet valve
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17 with the compensating vessel 7. Two parallel-disposed metering pumps 33 and
34 are furthermore connected to the pulsation damper 30, and are~ respectively,
located between two manually actuatable pump cocks or taps 35 and 36, on the
one hand, and 37 and 38, on the other hand. The parallel branches formed,
respectively, of the one metering pump 33 and the pump cocks 35 and 36 as well
as of the other metering pump 34 and the pump cocks 37 and 38 terminate together
in an outlet line 39, at the other end of which an extruder 40 is connected.
A respective rotary speed-regulated direct-curre.nt drive 41, 42 is
associated with the metering pump 33 and 34. A potentiometer 43 ls provided to
adjust the nominal rotary speed of the direct-current drives 41 and 42 9 respec-
tively, Furthermore, the direct current drives 41 and 42 can be regulated in
dependence upon the rotary speed O F the screw in the extruder 40.
The actual measured value obtained from the liquid flow meter 28 is
compared in a non-illustrated comparator with a nominal value coming from the
potentiometer 43 or from the screw speed of the extruder 40, and fed to an
indicator or display 44 with adjustable tolerance indicia 44a, 44b. If the
comparison result should exceed one of these tolerance indicia 44a, 44b, then
a change-over would automatically occur from the particular metering pump 33
or 34 happening to be in operation at that time to the other metering pump 34
or 33, as the case may be, with the actuation of a fault signaling device 45.
In order to take into account the differing viscosities of various
liquid additives, a non-illustrated calibrating potentiometer is provided with
which the measurement value of the actual flow rate deviation displayed on the
indicatlng devi.ce 44 can be adjusted or matched (æero shift).
In a :Eurther development of the invention, a sensor may be introduced
for monitoring the interior space within the equipment housing 31 and which
actuates a suitable warning device upon the appearance of any possible additive
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vapo~s. Likewise, a further, suitable sensor may also be installed in the
immediate surroundings of the equipment housing 31.
The transfer pump l fills the storage vessels 12 and 13, respectively,
with additive from the supply vessel 3. In this regard, the additive is pumped
through the dirt filter 5 into the transfer line 6. The compensating vessel 7
located in the transfer line 6 is thereby necessarily filled with a defined
amount of liquid. The respective storage vessels 12 and 13 are filled auto-
matically from the transfer line 6 through the respective magnetic shutoff
valves 9 and 11 upon the transmission of a signal by the associated minimal
contacts 14b and 15b, respectively. In the case of a defect in one of these
magnetic shutoff valves 9 and 11, the storage vessels 12 and 13 are then filled
through the manually actuatable stopcocks 8 and 10, respectively. When the
liquid level in the storage vessels 12 and 13, respectively, reaches the level
of the ma~imal contacts 14a and 15a, respectively, the respective magnetic
shut-off valves 9 and 11 automatically close and the tr~nsfer pump 1 is auto-
matically switched off. The particular storage vessel 12 or 13 which has in
fact been freshly filled in the time interval is initially separated from the
further components of the metering device according to the invention by the
magnetic change-over valve 18. ~le freshly filled liquid gradually assumes the
temperature level of the inner space of the equipment housing 31. In the
interim, the lukewarm additive is conducted from the other storage vessel 12 or
13, which has not been freshly filled, through the magnetic change-over valve
18, the drain cock 19, the filter inlet cock 22, one of the purification filters
23 and 24 and the filter draln cock 25 to the distributor cock 26. The possible
by-pass lines can be set into operation when necessary. The additive travels
from the distributor cock 26 through the liquld flow meter 2~ into the
additional distributor cock 27. The measured value obtained thereby is fed,
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after processing, to the indicator device 44 as well as the metering pumps 33
and 34, respectively, for the hereinafore-described purposes. If necessary,
the by~pass line 28a can also be set in oReration. The additive is conducted
from the outlet of the distributor cock 27 to the pulsation damper 30~ The
pulsation damper 30, which is connected through the magnetic inlet valve 17 to
the compensating vessel 7, serves for preventing oscillations or vibrations
produced in the additive from the after-connected metering pumps 33 and 34,
respectively, from reaching the liquid flow meter 28 or permits them to reach
the flow meter 28 only in very damped condition. The common outlet line 39
connected to the respective metering pumps 33 and 34 leads to the extruder 40.
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