CA1124551A

CA1124551A - Metering device

Info

Publication number: CA1124551A
Application number: CA339,093A
Authority: CA
Inventors: Gert Winkler; Dieter Schmitz
Original assignee: KABEL-UND LACKDRAHTFABRIKEN GmbH
Current assignee: KABEL-UND LACKDRAHTFABRIKEN GmbH
Priority date: 1978-11-02
Filing date: 1979-11-02
Publication date: 1982-06-01
Also published as: EP0010743A1; DE2847431A1; EP0010743B1; JPS5565509A

Abstract

Abstract of the Disclosure:
Device for metering a liquid additive including two parallel storage vessels, means including parallel stop cocks and parallel magnetic shut-off valves, respectively, for connecting the storage vessels to one another, two parallel purification filters, means in-cluding 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-meter, the purification 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 compen-sating vessel to the outlet end of the pulsation damper, and a parallel assembly of similar metering pumps cooperatively connected through an outlet line to an extruder being also connected to the inlet end of the pulsation damper.

Description

~ 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 ~ , , ' , 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. : ' .
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 ,~1 ', ' 4S~

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 7 i .

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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 -8- . ;
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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 ~Zl-~S~

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 ~ ) -11-: j,, ~2~

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, ' ' ~2~

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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Device for metering a liquid additive comprising two parallel storage vessels, means including parallel stop cocks and parallel magnetic shut-off valves, respectively, for connecting said 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 said storage vessels to said purification filters, said drain cocks being located downstream from said 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, said purification filters being connected through said parallel arrangement to said inlet end of said pulsation damper, a compensating vessel, means including a magnetic inlet valve connecting said compensating vessel to said outlet end of said pulsation damper, and a parallel assembly of similar metering pumps cooperatively connected through an outlet line to an extruder and being also connected to said inlet end of said pulsation damper.

2. Device according to claim 1 wherein said storage vessels and said pulsation damper are located at the same height level.

3. Device according to claim 1 including a sensor, respectively, dis-posed in each of said storage vessels.

4. Device according to claim 3 wherein said sensor in each of said storage vessels has a maximal contact and a minimal contact.

5. Device according to claim 4, including liquid-level indicating means, and wherein the maximal contacts of the respective sensors are collected galvanically to said magnetic shut-off valves, said transfer pump and said liquid-level indicating means.

6. Device according to claim 4, including liquid-level indicating means, and wherein the minimal contacts of the respective sensors are galvanically connected to said magnetic shut-off valves, said transfer pump, said liquid level indicating means, said magnetic inlet valve and said magnetic change-over valve.

7. Device according to claim 1 wherein said magnetic change-over valve is connected to said storage vessels downstream therefrom in direction of travel of a liquid therefrom, one of said drain cocks being serially connected with said magnetic change-over valve.

8. Device according to claim 7 wherein said one of said drain cocks is manually actuatable, and two others of said drain cocks are also manually actuatable and connected in parallel with said one of said drain cocks.

9. Device according to claim 8 wherein all three of said drain cocks are cooperatively connected to a filter inlet cock.

10. Device according to claim 9 including a filter outlet cock, both said filter inlet and said filter outlet cocks being constructed as manually actuatable three-way cocks, and two purification filters connected in parallel between said filter inlet cock and said filter outlet cock.

11. Device according to claim 10 including two distributor cocks mutually connected by a by-pass line and connected to said filter outlet cock downstream therefrom.

12. Device according to claim 11 including a liquid flow meter received in a housing, said liquid flow meter being connected in parallel with said by-pass line.

13. Device according to claim 10 wherein one of said distributor cocks has an inlet connected directly to said filter outlet cock, and the other of said distributor cocks has an outlet connected to a pulsation damper.

14. Device according to claim 13 including two metering pumps con-nected in parallel with said pulsation damper, and two manually actuatable pump cocks associated with each of said metering pumps.

15. Device according to claim 14 including an extruder and an outlet line connected to said extruder, both of said metering pumps being connected in common with said outlet line.

16. Device according to claim 13 including two distributor cocks mutually connected by a by-pass line and connected to said filter outlet cock downstream therefrom, a liquid flow meter received in a housing and connected in parallel with said by-pass line, and a sensor, respectively, disposed in each of said storage vessels, said storage vessels, said sensors, said magnetic change-over valve, said three drain cocks, said filter inlet cock, said purification filters, said filter outlet cock, said distributor cocks, said liquid flow meter, said by-pass line, said housing for said flow meter, and said pulsation damper being all received in an equipment housing.

17. Device according to claim 14, including a potentiometer operatively associated with said metering pumps for regulating rotary speed thereof.

18. Device according to claim 11, including a screw extruder connected to said metering pumps, and wherein the rotary speed of said metering pumps is regulated in accordance with the rotary speed of the extruder screw.

19. Device according to claim 18 including an indicator device connected to at least any one of said liquid flow meter, said potentiometer and said extruder screw.

20. Device according to claim 19 wherein said indicator device has tolerance indicia thereon, said magnetic change-over valve being actuatable in response to an indicator value exceeding one of said tolerance indicia for changing over from the then operating metering pump to the other metering pump.

21. Device according to claim 19 including a calibrating potentiometer operatively associated with said indicator device for shifting the zero point thereof.

22. Device according to claim 16 including sensor means within said equipment housing for monitoring a concentration of additive vapor within said equipment housing.

23. Device according to claim 16 including sensor means outside said equipment housing for monitoring a concentration of additive vapor outside said equipment housing.