CA1075489A - Measurement and control of multicomponent liquid systems - Google Patents
Measurement and control of multicomponent liquid systemsInfo
- Publication number
- CA1075489A CA1075489A CA254,503A CA254503A CA1075489A CA 1075489 A CA1075489 A CA 1075489A CA 254503 A CA254503 A CA 254503A CA 1075489 A CA1075489 A CA 1075489A
- Authority
- CA
- Canada
- Prior art keywords
- heat
- transit time
- liquid
- impulse
- flowrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
- G01F1/7044—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter using thermal tracers
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D11/00—Control of flow ratio
- G05D11/02—Controlling ratio of two or more flows of fluid or fluent material
- G05D11/13—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means
- G05D11/131—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means by measuring the values related to the quantity of the individual components
- G05D11/132—Controlling ratio of two or more flows of fluid or fluent material characterised by the use of electric means by measuring the values related to the quantity of the individual components by controlling the flow of the individual components
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D7/00—Control of flow
- G05D7/06—Control of flow characterised by the use of electric means
- G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
- G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
- G05D7/0635—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Fluid Mechanics (AREA)
- Measuring Volume Flow (AREA)
- Control Of Non-Electrical Variables (AREA)
- Accessories For Mixers (AREA)
- Coating Apparatus (AREA)
- Nozzles (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The instant invention provides an improved method for determining the streaming velocity of a streaming liquid by injecting a thermopulse into the liquid and measuring Its transit time. The pulse is detected by its ascending flamk at downstream points and by its ascending or descending flank at its point of injection.
For short transit times, provision is made to eliminate the neat up time of the heating wire imparting the pulse from the transit time measurement. The liquid may stream continuously or discontinuously, and if the latter, provision is made to decay measurement on initiation of flow until the flow pattern has stabilized. The time is determined by counting pulses from a pulse generator during the period the pulse is traveling between the point of injection and a detection point or between two detection points. This procedure enables more precise measurement of flow than has heretofor been possible.
The present invention is also concerned with a method and an apparatus which permit accurate and reproducible dosing for multicomponent liquid systems. Previously known systems were dependent upon such variables as pump pressure, density, viscosity and temperature of the components but the present invention provides a mon-itoring and metering system independent of these variables and is able to provide reproducible dosing at the low (50 to 200 cm3/min, for example) flow rates utilized in spray lacquering. The method is based on the fact that the particular components are conveyed through separate pipes into a mixing chamber.
The flow rate at least one of the pipes is determined by the above procedure and the flow in the other pipes is then adjusted automatically to be in a fixed ratio to the first flow. The so-measured transit time is converted into an inversely proportional voltage and the flow rate in the other pipes is adjusted proportionally to this voltage.
An apparatus is provided for practicing the method. The apparatus comprises flow measuring elements which are electrical connected in the pipes leading to the mixing chamber.
The instant invention provides an improved method for determining the streaming velocity of a streaming liquid by injecting a thermopulse into the liquid and measuring Its transit time. The pulse is detected by its ascending flamk at downstream points and by its ascending or descending flank at its point of injection.
For short transit times, provision is made to eliminate the neat up time of the heating wire imparting the pulse from the transit time measurement. The liquid may stream continuously or discontinuously, and if the latter, provision is made to decay measurement on initiation of flow until the flow pattern has stabilized. The time is determined by counting pulses from a pulse generator during the period the pulse is traveling between the point of injection and a detection point or between two detection points. This procedure enables more precise measurement of flow than has heretofor been possible.
The present invention is also concerned with a method and an apparatus which permit accurate and reproducible dosing for multicomponent liquid systems. Previously known systems were dependent upon such variables as pump pressure, density, viscosity and temperature of the components but the present invention provides a mon-itoring and metering system independent of these variables and is able to provide reproducible dosing at the low (50 to 200 cm3/min, for example) flow rates utilized in spray lacquering. The method is based on the fact that the particular components are conveyed through separate pipes into a mixing chamber.
The flow rate at least one of the pipes is determined by the above procedure and the flow in the other pipes is then adjusted automatically to be in a fixed ratio to the first flow. The so-measured transit time is converted into an inversely proportional voltage and the flow rate in the other pipes is adjusted proportionally to this voltage.
An apparatus is provided for practicing the method. The apparatus comprises flow measuring elements which are electrical connected in the pipes leading to the mixing chamber.
Description
Mo-1633-Ca - LeA 16,529-Ca ~5~'3 MEASUREMENT AND CONTROL OF M~LTICOMPONENT LIQUID SYSTEMS
ACKGROUND OF THE INVENTION
The monitoring of fluid flow is important in a wide variety of fields. An application of particular interest has been determining the volumetric throughput of paint in spray painting. A number of methods for such monitoring have been proposed in the past including devices mechanically moved by the streaming fluid such as paddle wheels and the measurement of the transit time Of tracers such as heat pulses injected into streaming fluid. However, the precision and dependability of these methods has been found to be inadequate in certain ' applications. For instance, in spray painting with two component lacquer systems such as polyurethanes, it is important to control the ratio of the two components within narrow limits or a serious loss of quality may be experienced. To achieve this control, it is important to very precisely monitor the flow of one component and adjust the flow of the other component accordingly.
Prior art monitoring processes have been found to be insufficiently accurate or reproducible particularly in -~ the low output rates (50 to 200 cm3/min) encountered in spray lacquering and coating. Consequently, the two component dosing apparatus known and used hitherto does not meet these requirements. All pressure supplying pumps are susceptible to faults when used with abrasive and sediment-forming materials. Moving parts wear and lose theix tightness, thus altering the preset quantity ' . 'i~
.:
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ratio.
The simplest method of dosing a liquid by the application of a constant over-pressure to a liquid in a container does not work with two component installations. It has been found that in mixing process pressure fluctuations take place in the mixing chamber, affecting the quantity flowing into the mixing chamber.
In addition, pressure and thus flowrate fluctuations can occur in all pipes through leakage and changes of -10 viscosity, which exceed the permissible tolerance of the quantity ratio.
It is an object of this invention to provide a method of monitoring the streaming velocity in fluid systems which is both accurate and reproducible. It is a further object to provide a method which can determine the streaming velocity very quickly allowing almost - continuous monitoring. It is a further object of the invention to provide a dosing method for multicomponent liquid systems, which permits an accurate and reproducible dosing independent of pump pressure, density, viscosity and temperature of the components. This concerns predominately low output rates (50 to 200 cm /min per component) which, for example, are usual in spray lacquering and coating. The reproducibility of the dosing should not be affected by liquid components containing abrasive pigments.
.
Mo-1633-Ca LeA 16,529-Ca -2-:, .
1C~759~9 SUMMARY OF THE INVENTION
In order to determine the streaming velocity of a fluid according to the present invention, a heat pulse is injected into the fluid and its transit time is measured over some fixed distance. The arrival of the heat pulse at the downstream measurement point is deter-mined by detecting the ascending flank of the pulse. If the transit time is determined from the point of pro-duction to a downstream detection point, either the ascending or descending flank of the heat pulse may be used to initiate the measurement. On the other hand, if the transit time is determined between two points downstream of the point of injection, the measurement is initiated by the arrival of the ascending flank at the first or more upstream of these points. The transit time is determined by digitally measuring the interval between the first and subsequent detection of the heat pulse. Of course, the transit time can be determined between more than two consecutive detection points downstream of the point of injection, using the arrival of the ascending flank of the heat pulse as the detection event.
According to the invention, there is also provided a method ~or dosing multicomponent liquid systems into a mixing chamber, in which the components are conveyed through separate pipes to the mixing chamber, wherein a heat pulse is injected into the liquid flowing in at least one of the pipes and the transit time determined as described above. The measured transit time is then ' ,' Mo-1633-Ca LeA 16,529-Ca ~ j, ~54~39 converted into a voltage which is proportional to the flowrate of the liquid in said pipe and the flowrate in the other pipes is controlled proportionally to this voltage.
According to a preferred embodiment the heat impulse is detected at only one point in the pipe downstream of the first point. The transit time is then the time taken by the heat impulse to travel the distance between the first point where the heat impulse is produced and the second point where the heat impulse is detected.
Alternatively the heat impulse is detected sequent-ially at a series of points in the pipe downstream of the ` first point. In this case the transit time is the time taken by the heat impulse to travel the distance between atleasttwo consecutive points downstream of the first point. The response time of measurement and thus the recovery time of the control device can be improved when the transit time is measured successively between more than two consecutive detection points downstream in the pipe.
In the field of lacquer coating the lacquer components are frequently not continuously but inter-mittently conveyed; e.g when a manually operated ~' 25 spraying gun is used. Pursuant to the present ' invention and in consideratlon of this object the heat impulse is injected into the pipe as soon after the restoration of flow as a stabilized flow pattern has become established.
Mo-1633-Ca eA 16,529-Ca -3a-. . , . :
~)75~13g It has been found that the accuracy of transit timemeas~irement can be improved when the transit time is determined by measuring the time lag ~ th~ moment where the ascending or descending flank Or the heat impulse appears at the first point and the moment where the ascending flank Or the heat impulse ~ ' arrives at the second point. Thus at the rirst point it is not ~' critical which flank of the heat impulse is used for measurement whereas at the second point the steep temperature increase at the ascendin~ flank, i.e. the front flank of the heat impulse lo is to be detect,ed and used ror further signal processing. It is evident that this embodiment may also be extended to the previousl,v described method where the travelling heat impulse is detected at more than one point downstream Or the first point. This means that the transit time is determined by measur- ~ ;
1 r- ing the time lag at the moments where the ascending flank o~
the heat impulse appears at two different other points down-stream of ~aid first point.
It is advantageous if the transit time measurement is effected periodically by periodically in~ecting a heat impulse at said first point.
For the purpose of providing a continuous signal ror the control member it has been proven successful to store electrically the instantaneous flowrate obtained from a measure-ment of transit time of an individual heat impulse until the 2C measurement of transit time is effected with the following heat impulse. In particular the storage of measurement is helpful when the components are periodically conveyed. In this case the value o~ the last measured flowrate is electrically stored and the flowrate in the other pipes is controlled in the ~ollowing ~e A 16,529 - 4 -, '' ' .' ' ." ~ ' ' 1~7~4~3~
period of conveyance with this measurement result until asubsequent measurement of flowrate is taken.
In one embodiment of the invention the transit time is digitally measured in at least one pipe by supplying impulses at a constant pulse frequency to an impulse counter for the period where the heat impulse travels from the first point to one of the other points or the distance between two successive other points. The counter content is then converted into a digitally quantity in the binary code which is proportional to the flowrate and thereafter reconverted into an analogous signal for actuating control means in the other pipes.
If the method according to the invention is applied to a two component system, the transit time measurement takes place in one pipe leading to the mixing chamber, while the flowrate in the other pipe is adjusted accord-ingly. The two flowrates are then always in a fixed ratio to one another independent of the absolute throughput A further modification of the invention comprises injecting periodically heat impulses and triggering a new heat impulse at the first point when the heat impulse - is detected at the second point. The resulting impulse frequency can then be used as a measure of the flowrate.
According to the invention there is also provided an apparatus for carrying out the method, comprising a mixing chamber, a plurality of pipes connected to the mixing chamber, in each of which is arranged an electrically activated dosing device, and in a further pipe connected to said mixing chamber a heating wire arranged in at least one of the pipes and downstream of the heating wire a ~ thermoelectric heat sensor, the heat sensor being ; electrically connected to an amplifier and a ; LeA 16,529-Ca -5-d~ J~
., - ~' ' ~ " '' ~L~75~
voltage compara-tor, means for producing periodic heat impulses by passing a current through the heating wire, an electric pulse generator supplying pulsesinto a counter during the transit time, during which a heat impulse travels from the heating wire to the thermoelectric sensor, a storing unit for storing the counter content until the next following heat impulse reaches the thermoelectric sensor, a code-converter for converting the counter content into a quantity in the binary code, which is proportional to the flowrate, a digital analog converter for reconvert-ing this quantity into an analogous signal and amplifier means for amplifying the analogous signal, which is connected to electrically activated dosing devices in the other pipes, the dosing rate of which is proportional to the voltage applied.
Preferably the apparatus is provided with a heating wire having a weight of less than 15 mg and means for periodically discharging a condensor through the heating wire within a few milliseconds. The duration of the heat impulses is within the range from 5 to 100 ms. In practice the distance between the heating wire and the thermoelec-tric heat sensor may be within the range from 5 to 500 mm.
As a thermoelectric heat sensor a differential thermocouple has been proven particularly successful.
Investigations of lacquer flow conditions have shown that the reciprocal of the flowrate and the transit time are not always proportional to each other but are correlat-ed by a non-linear function. To resolve this difficulty ; the code-converter in the apparatus is programmed to ac-count for the particular function between the flowrate and the transit time to yield finally a quantity ; which is proportional to the flowrate.
LeA 16,529 -6-~?? ~i ~7~4~39 _IEF DESCRIPTION OF THE DRAWINGS_ Figure 1 is a schematic representation of a two component control system, which is a preferred embodiment oE the present invention.
Figure 2 is a schematic representation of a particu-lar embodiment of sensing the flow in a pipe.
DETAILED DESCRIPTION OF THE INVENTION
The transit time measurement section is advantageously designed so that the impulse duration of the heat impulse is from 5 to 100 ms and the distance between the heating wire and the heat sensor is in the range of from 5 to 500 mm.
An important advantage of the method according to the inventlon is that precisely working dosing pumps are not required. Such pumps are generally very susceptible to faults.
Moreover the flow rate regulation according to the invention works without moving parts and is independent of the pressure, the optical transparency, the electrical conductivity and the viscosity of the components. Very low flowrates can also be dosed, since the dead volume of the measuring device is very low. Because of its small structural volume, the transit time measuring section and thus the regulation device can be fitted to hand operated mixing heads. The simple construction provides for trouble free exchange and cleaning.
In the accompanying drawings:
~' LeA 16,529-Ca -7-. j ., '' ' , ' . : ~
~ 75~
In Figure 1 a first component, e.g. a solution of a polyester resin containing hydroxyl groups with a 60~
solids content, is conveyed through pipe 1 and a second component, e.g. a polyisocyanate based hardener, is conveyed through a second pipe 2 into a mixing chamber 3.
The mixing chamber 3 is direc-tly connected to a spray gun. The components are conveyed by the application of an air or nitrogen over-pressure in an enclosed storage tank or out of ring pipes as is customary in the motor industry The ratio of the flowrates of the two components must always bekeptconstant to assure a uniform quality of the lacquering. To measure and regulate the quantity flow ratio a platinum heating wire 4 of 0.25 mm diameter in the form of a coil having five turns with a diameter of 2 mm, is incorporated in the center of the pipe l.This heater i$ heated up within a few milliseconds periodically or aperiodically by current impulses generated by discharging a condensor via the heating wire. Typical data for the platinum wire are:
Resistance 1.5 Ohm, weight 10 mg, pulse voltage 5 volts, pulse duration 50 ms. The discharge of the condensor is controlled via a transistor switch by the power amplifier 6 which is fed by an impulse generator 5 (tact generator). The ., LeA 16,529-Ca -8-~0754~39 heat pulse produced in this manner, is imparted to the central portion of the streaming liquid. This partion is then carrled along with the rlow as a heat plug. The heat plug after travel-ling ror the period of the transit time TJ reaches the thermo-electric heat sensor 7 incorporated in the center Or the flow.
The transit time T is directly proportional to the dlstance between the heater and the thermoelectric sensor 7 and inversely proportional to the streaming velocity and thus the flowrate.
In a preferred embodiment the distance between heater and sensor is in the range of 40 - 50 mm; however this distance may be varied ~or obtaining a higher accuracy or shorter measuring time. The heat sensor 7 is a differential thermocouple element with a very low respon6e time, which ensures that slow changes in the basic temperature of the liquid have no erfect o~ the 1~ measurement. The temperature rise as the heat plug flows past is recorded substantially without delay.
When using a device with the previously indicated data~ the maximum temperature at the dif~erential thermoccuple is reached within 20 - 100 ms depending on the streaming velocity.
The voltage produced at the di~erential couple element 7 is amplified by a chopper ampli~ier 8 with an amplification > 104 - so that a temperature increase Or 1 C at the di~erential thermo-couple i5 alread~ sufficient to activate the threshold comparator 9~ The threshold value of the comparator 9 is ad~usted to such a .. . .. . . . ..
l-ow voltage that the steep temperature increase at the ascending flank of the received thermopulse at the thermocouple acti~ates the comparator almost immediately to switch. It has been Le A 16J529 - 9 -~ - , :: - ' : ' ~L~754~39 surprisingly found that a more precise measurement o-f transit time can be obtained when using the ascending flank, i.e. the front flank of the thermoimpulse to excite the comparator 9.
The transi-t time of the heat plug is now digitally determined. Simultaneously with the current impulse through the heating wire 4, a bistable multivibrator 11 is set and is reset on receipt of the signal from the comparator 9. The period during which the bistable monovibratorll is set, corresponds to the transit time of the heat plug through the pipe 1 and is inversely proportional to the flowrate of the component in the pipe.
The measurement of the transit time is performed in the following manner. During the set time of the multivibrator 11 pulses from an impulse generator 13 are fed into an impulse counter 14 through a gate switch 12.
The counter 14 is each time set to ~ero by a signal supplied from the impulse generator 5 at the time of producing a new heat pulse. The pulses previously counted during a measuring cycle are temporarily stored in a digital store 15 until the next measuring cycle. This storing is necessary to deliver to the circuit an uninterrupted signal for controlling the dosing pump 23.
~ Storing of the counter content is also of particular '~ 25 importance when the components in the pipes are not continuously but periodically conveyed (cycling on-off operation). The value of the last measured flowrate is ` then stored in another digital storing unit (not shown) and the flowrate in the other pipes is controlled in the following period of conveyance on the basis of the stored value until a subsequent measurement of flowrate is taken.
LeA 16,529-Ca ~10-....
~7548~
To convert the transit times measured into flowrates a permanently programmed ROM-code co~verter 16 is used ("read only memory"). The counter content Or the pulse counter 14 indi-~ates rOr every measuring cycle the address from which the cl flowrate may be read from the ROM-element. Address and flow quantity are correlated previously by reading the program into the ROM. Normally the flowrate is inversely propor-tional to the address. However by modifying the program of the ROM,corrections resulting from the particular flow profile can lo be taken into account. Such corrections are for instance neces-sary in the case o~ liquids showing structural viscosities (non Newtonian liquids). The reciprocal Or the flowrate and the transit time are then no longer correlated by the usual linear f~nction. It is however possible by appropriately programming the ROM to obtain a correct flowrate measur~ment even under these unusual circumstances. Also corrections may be employed for compensating non linear ef~ects Or the dosing pump 23.
- For direct digital indication Or the flow-rate in pipe 1 the output of the code converter 16 is ~:~
connected to a numerical indicator unit 17. For analogue indication and to obtain a signal for control purposes the digital output signal of the code converter 16 is converted by a digital analogue converter 18 into an analogue voltage.
This voltage is passed through a voltage divider 20, by means of which the desired ratio between the flowrate of the liquid in the rirst pipe 1 and the flowrate to be regulated in the second pipe 2 is preselected. The regulation of the second Le A 16,529 : '.
component takes place by feeding the nominal value of the voltage coming from the voltage divider 20 to a proportion-al power amplifier 21, which supplies the drive motor 22 for a dosing pump 23 in pipe 2. Instead of a dosing pump (constant displacement pump), a motor-driven regulator valve or aperture can also be used.
If the device is operated with periodic heat pulses the function of the device is monitored by a retrigger-able monovibrator 24. If the liquid is streaming, voltage pulses corresponding to the heating cycles must arrive at the comparator 9. These voltage pulses are setting continuously the retriggerable monovibrator 24. In the event of interruption of the impulse sequence (e.g. caused by a defect in the heating wire 4, the thermocouple element 7, impulse amplifier 8, or by a flow stoppage) an alarm device 25 is activated. If the flow is stopped by ; intention, e.g. in the case of intermittently lacquer spraying, the monitoring unit 24 is disconnected for the time of interruption. When operating the device inter-mittently the outlet nozzle 26 of the mixing chamber 3 is provided with a shutting valve 27 which controls a switch 28, being connected to the pulse generator 5. By a switch 28 the impulse generator 5 is then energized and activated in such a manner that almost simultaneously at the moment of restoring the flow in pipe 1 by opening the valve 27 the pulse generator 5 is started to impart a thermoimpulse via power amplifier 6 and heating wire 4 to the streaming liquid in pipe 1. It has been observed in this connection that the measurement of transit time may be obscured by an unstable flow pattern just after restoring the flow by opening the valve 27. Therefore an adjustable delay unit 29 is introduced in the line between the LeA 16,529-Ca -12-,,,,~
'' ' .
~07~i489 ~nechanical switch 28 and the impulse generator 5. The delay is ad~justed to such a value (in the order Or a rew millisecond~) tha~ the ~1rst thermoimpulse is not till then in~ected when the irregular rlow has been disappeared and steady state con-ditions are prevailing again in pipe 1. It has been found that the period Or restoring the steady state conditions is usually very short, i.e. in the order of a rew milliseconds.
According to a modi~ied embodiment Or the invention a ser~es Or dif~erential thermocouples 7 is arranged within lo the pipe 1 downstream Or the heating wire 4. The thermoimpulse then passes sequentially the series of thermocouples, produc-ing successive electric pulses. With this device a shorter - response time and higher accuracy of transit tlme measurement can be obtained which is however counterbalanced a more complex and expensive measuring device. The transit time of the thermoi~pulse is then measured between two successive ;
thermocouples in pipe 1. The distances between the sensors may be very small (i.e. in the order of 1 cm), since only the passage Or the steep flank o~ the heat pulse is used ~or signal processing. The measurement is carried out with an electronic circuit which is very similar to that which has already been described. When the thermoimpulse passes the ~ first thermocouple, pulses are counted at a constant rate - into counter 14 until the thermoimpulse arrives at the second thermocouple. Signal processing ls then per~ormed in the same manner as described above in connection with ~igure 1. This embodiment is particular useful e.g. with lacquer spraying in the automotive industry when the dosing device is operated for very short periods (C 1 s) and more than Le A 16,529 - 13 -1~7S4~39 one rlow measurement is required withln said period Or operation. When using more than two thermocouples and taklng successive measuring values for the transit time along the series Or thermocouplesJ a multiplexer may be used to switch the input Or the circuit (preamplirier 8) to successive ther-mocouples in pipe 1.
In one embodi~ent of the control circuit instead of the analogue quantity regulation, direct digital regulation is implemented. For this purpose a frequency proportional control lo motor (e~g, s,tep~in~ ~otorl i~ us~ed tQ drive the dos,ing pump 23, hei,ng fed.directl~ with the a,~pli~ied digital output signa,1 o~ the code c~nvexter 16~ ., A variant of the re.gulation device according to the invention for a two component system involves incorporating a transit time measurement section in both pipes and regulating - the flowrate in both pipes. With this embodiment not only the quantity ratio of the components but also the absolute quantity of the finished mixture can be maintained constant.
~ further possibility of signal processing is schematically shown in Figure 2, The voltage impulse generated by the heat plug is here used to trigger a new heat impulse in the impulse generator 5; i.e~ each heat plug arriving at the thermocouple element 7 immediately trigyers off a new heat impulse at the heating wire 4. The resultant impulse frequency is directly proportional to t~e flowrat~ i~ the pipe 1. It can be used in a similar manner, as already described in the first embodiment, for the regulation of the second component.
Ls A 16,529 - 14 -.
~075~89 With the arrangement described with reference to Figure 1, ~wo component polyurethane lacquers were produced and pro-cessed ready for spraying. One component contained a polyester solution wlth pigments and abrasive additives (e.g. piqments containing SiO2), while the other component consisted of a hardener solution comprislng polyisocyanates. The dosing of such mixtures is normally difficult on account of corrosion at the measuring and dosing elements. No indication of corrosion was observed on the tra,ns,it ti,me mea,suring section ~ven after ' a long period of operation. It is significant that the measur-ing element has no nloving par,ts~ Fx cleaning pu~poses it can be easily installed and re,movede Because of the measure~ent principle, the visco~ity - in contrast with most other measuring met;lods ~or flowrate is not included in the measurement.
According to the invention no difficulties occur in the dosing of liquids having a viscosity of from 50 to 2000 cP and flow-rates of from 20 to 10a0 cm3/min per component.
The method according to the invention was also tested in the production of polyurethane foams. For this purpose a reaction mixture of diisocyanates, polyols and water together with emulsifiers, dispersion ayents and catalysts was produced (see Kunststoff - Handbuch, Vol. 7, Polyurethane, Karl Hanser Verlag Munchen 1966, pages 144 - 149). For the production of polyurethane foams, as the first main component polyhydroxyl compounds having at least two hydroxyl groups of a molecular weight of from 62 to 10,000, preferably 62 to 5000 are used;
e.g. polyesters, polyethers, polythioethers, polyacetals, poly-carbonates, polyester amides having at least 2, usually from Le A 16,529 - 15 - :
~754~3~
ACKGROUND OF THE INVENTION
The monitoring of fluid flow is important in a wide variety of fields. An application of particular interest has been determining the volumetric throughput of paint in spray painting. A number of methods for such monitoring have been proposed in the past including devices mechanically moved by the streaming fluid such as paddle wheels and the measurement of the transit time Of tracers such as heat pulses injected into streaming fluid. However, the precision and dependability of these methods has been found to be inadequate in certain ' applications. For instance, in spray painting with two component lacquer systems such as polyurethanes, it is important to control the ratio of the two components within narrow limits or a serious loss of quality may be experienced. To achieve this control, it is important to very precisely monitor the flow of one component and adjust the flow of the other component accordingly.
Prior art monitoring processes have been found to be insufficiently accurate or reproducible particularly in -~ the low output rates (50 to 200 cm3/min) encountered in spray lacquering and coating. Consequently, the two component dosing apparatus known and used hitherto does not meet these requirements. All pressure supplying pumps are susceptible to faults when used with abrasive and sediment-forming materials. Moving parts wear and lose theix tightness, thus altering the preset quantity ' . 'i~
.:
'`, ~ , ' :
~C~75~
ratio.
The simplest method of dosing a liquid by the application of a constant over-pressure to a liquid in a container does not work with two component installations. It has been found that in mixing process pressure fluctuations take place in the mixing chamber, affecting the quantity flowing into the mixing chamber.
In addition, pressure and thus flowrate fluctuations can occur in all pipes through leakage and changes of -10 viscosity, which exceed the permissible tolerance of the quantity ratio.
It is an object of this invention to provide a method of monitoring the streaming velocity in fluid systems which is both accurate and reproducible. It is a further object to provide a method which can determine the streaming velocity very quickly allowing almost - continuous monitoring. It is a further object of the invention to provide a dosing method for multicomponent liquid systems, which permits an accurate and reproducible dosing independent of pump pressure, density, viscosity and temperature of the components. This concerns predominately low output rates (50 to 200 cm /min per component) which, for example, are usual in spray lacquering and coating. The reproducibility of the dosing should not be affected by liquid components containing abrasive pigments.
.
Mo-1633-Ca LeA 16,529-Ca -2-:, .
1C~759~9 SUMMARY OF THE INVENTION
In order to determine the streaming velocity of a fluid according to the present invention, a heat pulse is injected into the fluid and its transit time is measured over some fixed distance. The arrival of the heat pulse at the downstream measurement point is deter-mined by detecting the ascending flank of the pulse. If the transit time is determined from the point of pro-duction to a downstream detection point, either the ascending or descending flank of the heat pulse may be used to initiate the measurement. On the other hand, if the transit time is determined between two points downstream of the point of injection, the measurement is initiated by the arrival of the ascending flank at the first or more upstream of these points. The transit time is determined by digitally measuring the interval between the first and subsequent detection of the heat pulse. Of course, the transit time can be determined between more than two consecutive detection points downstream of the point of injection, using the arrival of the ascending flank of the heat pulse as the detection event.
According to the invention, there is also provided a method ~or dosing multicomponent liquid systems into a mixing chamber, in which the components are conveyed through separate pipes to the mixing chamber, wherein a heat pulse is injected into the liquid flowing in at least one of the pipes and the transit time determined as described above. The measured transit time is then ' ,' Mo-1633-Ca LeA 16,529-Ca ~ j, ~54~39 converted into a voltage which is proportional to the flowrate of the liquid in said pipe and the flowrate in the other pipes is controlled proportionally to this voltage.
According to a preferred embodiment the heat impulse is detected at only one point in the pipe downstream of the first point. The transit time is then the time taken by the heat impulse to travel the distance between the first point where the heat impulse is produced and the second point where the heat impulse is detected.
Alternatively the heat impulse is detected sequent-ially at a series of points in the pipe downstream of the ` first point. In this case the transit time is the time taken by the heat impulse to travel the distance between atleasttwo consecutive points downstream of the first point. The response time of measurement and thus the recovery time of the control device can be improved when the transit time is measured successively between more than two consecutive detection points downstream in the pipe.
In the field of lacquer coating the lacquer components are frequently not continuously but inter-mittently conveyed; e.g when a manually operated ~' 25 spraying gun is used. Pursuant to the present ' invention and in consideratlon of this object the heat impulse is injected into the pipe as soon after the restoration of flow as a stabilized flow pattern has become established.
Mo-1633-Ca eA 16,529-Ca -3a-. . , . :
~)75~13g It has been found that the accuracy of transit timemeas~irement can be improved when the transit time is determined by measuring the time lag ~ th~ moment where the ascending or descending flank Or the heat impulse appears at the first point and the moment where the ascending flank Or the heat impulse ~ ' arrives at the second point. Thus at the rirst point it is not ~' critical which flank of the heat impulse is used for measurement whereas at the second point the steep temperature increase at the ascendin~ flank, i.e. the front flank of the heat impulse lo is to be detect,ed and used ror further signal processing. It is evident that this embodiment may also be extended to the previousl,v described method where the travelling heat impulse is detected at more than one point downstream Or the first point. This means that the transit time is determined by measur- ~ ;
1 r- ing the time lag at the moments where the ascending flank o~
the heat impulse appears at two different other points down-stream of ~aid first point.
It is advantageous if the transit time measurement is effected periodically by periodically in~ecting a heat impulse at said first point.
For the purpose of providing a continuous signal ror the control member it has been proven successful to store electrically the instantaneous flowrate obtained from a measure-ment of transit time of an individual heat impulse until the 2C measurement of transit time is effected with the following heat impulse. In particular the storage of measurement is helpful when the components are periodically conveyed. In this case the value o~ the last measured flowrate is electrically stored and the flowrate in the other pipes is controlled in the ~ollowing ~e A 16,529 - 4 -, '' ' .' ' ." ~ ' ' 1~7~4~3~
period of conveyance with this measurement result until asubsequent measurement of flowrate is taken.
In one embodiment of the invention the transit time is digitally measured in at least one pipe by supplying impulses at a constant pulse frequency to an impulse counter for the period where the heat impulse travels from the first point to one of the other points or the distance between two successive other points. The counter content is then converted into a digitally quantity in the binary code which is proportional to the flowrate and thereafter reconverted into an analogous signal for actuating control means in the other pipes.
If the method according to the invention is applied to a two component system, the transit time measurement takes place in one pipe leading to the mixing chamber, while the flowrate in the other pipe is adjusted accord-ingly. The two flowrates are then always in a fixed ratio to one another independent of the absolute throughput A further modification of the invention comprises injecting periodically heat impulses and triggering a new heat impulse at the first point when the heat impulse - is detected at the second point. The resulting impulse frequency can then be used as a measure of the flowrate.
According to the invention there is also provided an apparatus for carrying out the method, comprising a mixing chamber, a plurality of pipes connected to the mixing chamber, in each of which is arranged an electrically activated dosing device, and in a further pipe connected to said mixing chamber a heating wire arranged in at least one of the pipes and downstream of the heating wire a ~ thermoelectric heat sensor, the heat sensor being ; electrically connected to an amplifier and a ; LeA 16,529-Ca -5-d~ J~
., - ~' ' ~ " '' ~L~75~
voltage compara-tor, means for producing periodic heat impulses by passing a current through the heating wire, an electric pulse generator supplying pulsesinto a counter during the transit time, during which a heat impulse travels from the heating wire to the thermoelectric sensor, a storing unit for storing the counter content until the next following heat impulse reaches the thermoelectric sensor, a code-converter for converting the counter content into a quantity in the binary code, which is proportional to the flowrate, a digital analog converter for reconvert-ing this quantity into an analogous signal and amplifier means for amplifying the analogous signal, which is connected to electrically activated dosing devices in the other pipes, the dosing rate of which is proportional to the voltage applied.
Preferably the apparatus is provided with a heating wire having a weight of less than 15 mg and means for periodically discharging a condensor through the heating wire within a few milliseconds. The duration of the heat impulses is within the range from 5 to 100 ms. In practice the distance between the heating wire and the thermoelec-tric heat sensor may be within the range from 5 to 500 mm.
As a thermoelectric heat sensor a differential thermocouple has been proven particularly successful.
Investigations of lacquer flow conditions have shown that the reciprocal of the flowrate and the transit time are not always proportional to each other but are correlat-ed by a non-linear function. To resolve this difficulty ; the code-converter in the apparatus is programmed to ac-count for the particular function between the flowrate and the transit time to yield finally a quantity ; which is proportional to the flowrate.
LeA 16,529 -6-~?? ~i ~7~4~39 _IEF DESCRIPTION OF THE DRAWINGS_ Figure 1 is a schematic representation of a two component control system, which is a preferred embodiment oE the present invention.
Figure 2 is a schematic representation of a particu-lar embodiment of sensing the flow in a pipe.
DETAILED DESCRIPTION OF THE INVENTION
The transit time measurement section is advantageously designed so that the impulse duration of the heat impulse is from 5 to 100 ms and the distance between the heating wire and the heat sensor is in the range of from 5 to 500 mm.
An important advantage of the method according to the inventlon is that precisely working dosing pumps are not required. Such pumps are generally very susceptible to faults.
Moreover the flow rate regulation according to the invention works without moving parts and is independent of the pressure, the optical transparency, the electrical conductivity and the viscosity of the components. Very low flowrates can also be dosed, since the dead volume of the measuring device is very low. Because of its small structural volume, the transit time measuring section and thus the regulation device can be fitted to hand operated mixing heads. The simple construction provides for trouble free exchange and cleaning.
In the accompanying drawings:
~' LeA 16,529-Ca -7-. j ., '' ' , ' . : ~
~ 75~
In Figure 1 a first component, e.g. a solution of a polyester resin containing hydroxyl groups with a 60~
solids content, is conveyed through pipe 1 and a second component, e.g. a polyisocyanate based hardener, is conveyed through a second pipe 2 into a mixing chamber 3.
The mixing chamber 3 is direc-tly connected to a spray gun. The components are conveyed by the application of an air or nitrogen over-pressure in an enclosed storage tank or out of ring pipes as is customary in the motor industry The ratio of the flowrates of the two components must always bekeptconstant to assure a uniform quality of the lacquering. To measure and regulate the quantity flow ratio a platinum heating wire 4 of 0.25 mm diameter in the form of a coil having five turns with a diameter of 2 mm, is incorporated in the center of the pipe l.This heater i$ heated up within a few milliseconds periodically or aperiodically by current impulses generated by discharging a condensor via the heating wire. Typical data for the platinum wire are:
Resistance 1.5 Ohm, weight 10 mg, pulse voltage 5 volts, pulse duration 50 ms. The discharge of the condensor is controlled via a transistor switch by the power amplifier 6 which is fed by an impulse generator 5 (tact generator). The ., LeA 16,529-Ca -8-~0754~39 heat pulse produced in this manner, is imparted to the central portion of the streaming liquid. This partion is then carrled along with the rlow as a heat plug. The heat plug after travel-ling ror the period of the transit time TJ reaches the thermo-electric heat sensor 7 incorporated in the center Or the flow.
The transit time T is directly proportional to the dlstance between the heater and the thermoelectric sensor 7 and inversely proportional to the streaming velocity and thus the flowrate.
In a preferred embodiment the distance between heater and sensor is in the range of 40 - 50 mm; however this distance may be varied ~or obtaining a higher accuracy or shorter measuring time. The heat sensor 7 is a differential thermocouple element with a very low respon6e time, which ensures that slow changes in the basic temperature of the liquid have no erfect o~ the 1~ measurement. The temperature rise as the heat plug flows past is recorded substantially without delay.
When using a device with the previously indicated data~ the maximum temperature at the dif~erential thermoccuple is reached within 20 - 100 ms depending on the streaming velocity.
The voltage produced at the di~erential couple element 7 is amplified by a chopper ampli~ier 8 with an amplification > 104 - so that a temperature increase Or 1 C at the di~erential thermo-couple i5 alread~ sufficient to activate the threshold comparator 9~ The threshold value of the comparator 9 is ad~usted to such a .. . .. . . . ..
l-ow voltage that the steep temperature increase at the ascending flank of the received thermopulse at the thermocouple acti~ates the comparator almost immediately to switch. It has been Le A 16J529 - 9 -~ - , :: - ' : ' ~L~754~39 surprisingly found that a more precise measurement o-f transit time can be obtained when using the ascending flank, i.e. the front flank of the thermoimpulse to excite the comparator 9.
The transi-t time of the heat plug is now digitally determined. Simultaneously with the current impulse through the heating wire 4, a bistable multivibrator 11 is set and is reset on receipt of the signal from the comparator 9. The period during which the bistable monovibratorll is set, corresponds to the transit time of the heat plug through the pipe 1 and is inversely proportional to the flowrate of the component in the pipe.
The measurement of the transit time is performed in the following manner. During the set time of the multivibrator 11 pulses from an impulse generator 13 are fed into an impulse counter 14 through a gate switch 12.
The counter 14 is each time set to ~ero by a signal supplied from the impulse generator 5 at the time of producing a new heat pulse. The pulses previously counted during a measuring cycle are temporarily stored in a digital store 15 until the next measuring cycle. This storing is necessary to deliver to the circuit an uninterrupted signal for controlling the dosing pump 23.
~ Storing of the counter content is also of particular '~ 25 importance when the components in the pipes are not continuously but periodically conveyed (cycling on-off operation). The value of the last measured flowrate is ` then stored in another digital storing unit (not shown) and the flowrate in the other pipes is controlled in the following period of conveyance on the basis of the stored value until a subsequent measurement of flowrate is taken.
LeA 16,529-Ca ~10-....
~7548~
To convert the transit times measured into flowrates a permanently programmed ROM-code co~verter 16 is used ("read only memory"). The counter content Or the pulse counter 14 indi-~ates rOr every measuring cycle the address from which the cl flowrate may be read from the ROM-element. Address and flow quantity are correlated previously by reading the program into the ROM. Normally the flowrate is inversely propor-tional to the address. However by modifying the program of the ROM,corrections resulting from the particular flow profile can lo be taken into account. Such corrections are for instance neces-sary in the case o~ liquids showing structural viscosities (non Newtonian liquids). The reciprocal Or the flowrate and the transit time are then no longer correlated by the usual linear f~nction. It is however possible by appropriately programming the ROM to obtain a correct flowrate measur~ment even under these unusual circumstances. Also corrections may be employed for compensating non linear ef~ects Or the dosing pump 23.
- For direct digital indication Or the flow-rate in pipe 1 the output of the code converter 16 is ~:~
connected to a numerical indicator unit 17. For analogue indication and to obtain a signal for control purposes the digital output signal of the code converter 16 is converted by a digital analogue converter 18 into an analogue voltage.
This voltage is passed through a voltage divider 20, by means of which the desired ratio between the flowrate of the liquid in the rirst pipe 1 and the flowrate to be regulated in the second pipe 2 is preselected. The regulation of the second Le A 16,529 : '.
component takes place by feeding the nominal value of the voltage coming from the voltage divider 20 to a proportion-al power amplifier 21, which supplies the drive motor 22 for a dosing pump 23 in pipe 2. Instead of a dosing pump (constant displacement pump), a motor-driven regulator valve or aperture can also be used.
If the device is operated with periodic heat pulses the function of the device is monitored by a retrigger-able monovibrator 24. If the liquid is streaming, voltage pulses corresponding to the heating cycles must arrive at the comparator 9. These voltage pulses are setting continuously the retriggerable monovibrator 24. In the event of interruption of the impulse sequence (e.g. caused by a defect in the heating wire 4, the thermocouple element 7, impulse amplifier 8, or by a flow stoppage) an alarm device 25 is activated. If the flow is stopped by ; intention, e.g. in the case of intermittently lacquer spraying, the monitoring unit 24 is disconnected for the time of interruption. When operating the device inter-mittently the outlet nozzle 26 of the mixing chamber 3 is provided with a shutting valve 27 which controls a switch 28, being connected to the pulse generator 5. By a switch 28 the impulse generator 5 is then energized and activated in such a manner that almost simultaneously at the moment of restoring the flow in pipe 1 by opening the valve 27 the pulse generator 5 is started to impart a thermoimpulse via power amplifier 6 and heating wire 4 to the streaming liquid in pipe 1. It has been observed in this connection that the measurement of transit time may be obscured by an unstable flow pattern just after restoring the flow by opening the valve 27. Therefore an adjustable delay unit 29 is introduced in the line between the LeA 16,529-Ca -12-,,,,~
'' ' .
~07~i489 ~nechanical switch 28 and the impulse generator 5. The delay is ad~justed to such a value (in the order Or a rew millisecond~) tha~ the ~1rst thermoimpulse is not till then in~ected when the irregular rlow has been disappeared and steady state con-ditions are prevailing again in pipe 1. It has been found that the period Or restoring the steady state conditions is usually very short, i.e. in the order of a rew milliseconds.
According to a modi~ied embodiment Or the invention a ser~es Or dif~erential thermocouples 7 is arranged within lo the pipe 1 downstream Or the heating wire 4. The thermoimpulse then passes sequentially the series of thermocouples, produc-ing successive electric pulses. With this device a shorter - response time and higher accuracy of transit tlme measurement can be obtained which is however counterbalanced a more complex and expensive measuring device. The transit time of the thermoi~pulse is then measured between two successive ;
thermocouples in pipe 1. The distances between the sensors may be very small (i.e. in the order of 1 cm), since only the passage Or the steep flank o~ the heat pulse is used ~or signal processing. The measurement is carried out with an electronic circuit which is very similar to that which has already been described. When the thermoimpulse passes the ~ first thermocouple, pulses are counted at a constant rate - into counter 14 until the thermoimpulse arrives at the second thermocouple. Signal processing ls then per~ormed in the same manner as described above in connection with ~igure 1. This embodiment is particular useful e.g. with lacquer spraying in the automotive industry when the dosing device is operated for very short periods (C 1 s) and more than Le A 16,529 - 13 -1~7S4~39 one rlow measurement is required withln said period Or operation. When using more than two thermocouples and taklng successive measuring values for the transit time along the series Or thermocouplesJ a multiplexer may be used to switch the input Or the circuit (preamplirier 8) to successive ther-mocouples in pipe 1.
In one embodi~ent of the control circuit instead of the analogue quantity regulation, direct digital regulation is implemented. For this purpose a frequency proportional control lo motor (e~g, s,tep~in~ ~otorl i~ us~ed tQ drive the dos,ing pump 23, hei,ng fed.directl~ with the a,~pli~ied digital output signa,1 o~ the code c~nvexter 16~ ., A variant of the re.gulation device according to the invention for a two component system involves incorporating a transit time measurement section in both pipes and regulating - the flowrate in both pipes. With this embodiment not only the quantity ratio of the components but also the absolute quantity of the finished mixture can be maintained constant.
~ further possibility of signal processing is schematically shown in Figure 2, The voltage impulse generated by the heat plug is here used to trigger a new heat impulse in the impulse generator 5; i.e~ each heat plug arriving at the thermocouple element 7 immediately trigyers off a new heat impulse at the heating wire 4. The resultant impulse frequency is directly proportional to t~e flowrat~ i~ the pipe 1. It can be used in a similar manner, as already described in the first embodiment, for the regulation of the second component.
Ls A 16,529 - 14 -.
~075~89 With the arrangement described with reference to Figure 1, ~wo component polyurethane lacquers were produced and pro-cessed ready for spraying. One component contained a polyester solution wlth pigments and abrasive additives (e.g. piqments containing SiO2), while the other component consisted of a hardener solution comprislng polyisocyanates. The dosing of such mixtures is normally difficult on account of corrosion at the measuring and dosing elements. No indication of corrosion was observed on the tra,ns,it ti,me mea,suring section ~ven after ' a long period of operation. It is significant that the measur-ing element has no nloving par,ts~ Fx cleaning pu~poses it can be easily installed and re,movede Because of the measure~ent principle, the visco~ity - in contrast with most other measuring met;lods ~or flowrate is not included in the measurement.
According to the invention no difficulties occur in the dosing of liquids having a viscosity of from 50 to 2000 cP and flow-rates of from 20 to 10a0 cm3/min per component.
The method according to the invention was also tested in the production of polyurethane foams. For this purpose a reaction mixture of diisocyanates, polyols and water together with emulsifiers, dispersion ayents and catalysts was produced (see Kunststoff - Handbuch, Vol. 7, Polyurethane, Karl Hanser Verlag Munchen 1966, pages 144 - 149). For the production of polyurethane foams, as the first main component polyhydroxyl compounds having at least two hydroxyl groups of a molecular weight of from 62 to 10,000, preferably 62 to 5000 are used;
e.g. polyesters, polyethers, polythioethers, polyacetals, poly-carbonates, polyester amides having at least 2, usually from Le A 16,529 - 15 - :
~754~3~
2 - 8, preferably, however, 2 hydroxyl groups. The second main component should preferably consist oE aliphatic, cyclo-aliphatic, araliphatic and aromatic polyisocyanates. In particular the technically easily obtainable polyisocyanates are used e.g. the 2,4- and 2,6-toluylene diisocyanates and any mixtures o~ these isomers and polyphenyl polymethane poly-isocyanates. The components must be very accurately dosed.
For this purpose the above described regulation system accord-ing to the principle of transit time measurement has proved lo very effective.
' .
Although the invention has been described in detail for the purpose of illustration, it is to be understood that yariations can be made therei~n by thQse skilled in the a~t without departing from the spirit ~nd scope o~ the invention except as it may be limited by the claims.
Le A 16,529 - 16 -.:
' ~7541~
SUPPLEMENTARY ~ISCLOSURE
This is a Supplementary Disclosure to Canadian Patent ~pplication Serial Number 254,503 filed June 10, 1976.
When measuring relatively short transit times (high streaming velocity or relatively short transit time measuring distance) the time constant for heating the heating means, e.g. a wire, is no longer small compared to the transit time, thus reducing the accuracy of the measurement. This error can be elim-inated by subtracting the heat up time of said means from the measured transit time. For instance, the circuit of Figure l can be modified so that the multivibrator is set at the initiation of the heat pulse (the pulse of electrical power to the heating wire 4) but the pulse counter15 is set to zero after a delay equal to the heat up time of the wire. In this way those pulses which are delivered through gate 12 ;; to the pulse counter during this heat up time are eliminated.
When measuring veIocity in intermittent flow systems it is o~ten necessary to delay the injection of a thermopulse for a substantial time after the indi-cation of flow if the measurement is to reflect steady state flowconditions. At flow rates of between 20 and 1000 cm3/minute the time for the restoration of a substantially stable flow pattern is between about 0.01 and 0.5 seconds and at flow rates of between 50 and 200 cm3/minute the time is between about 0.05 and 0.2 seconds.
.~j LeA 16,529-Ca -17-~ ~J~
For this purpose the above described regulation system accord-ing to the principle of transit time measurement has proved lo very effective.
' .
Although the invention has been described in detail for the purpose of illustration, it is to be understood that yariations can be made therei~n by thQse skilled in the a~t without departing from the spirit ~nd scope o~ the invention except as it may be limited by the claims.
Le A 16,529 - 16 -.:
' ~7541~
SUPPLEMENTARY ~ISCLOSURE
This is a Supplementary Disclosure to Canadian Patent ~pplication Serial Number 254,503 filed June 10, 1976.
When measuring relatively short transit times (high streaming velocity or relatively short transit time measuring distance) the time constant for heating the heating means, e.g. a wire, is no longer small compared to the transit time, thus reducing the accuracy of the measurement. This error can be elim-inated by subtracting the heat up time of said means from the measured transit time. For instance, the circuit of Figure l can be modified so that the multivibrator is set at the initiation of the heat pulse (the pulse of electrical power to the heating wire 4) but the pulse counter15 is set to zero after a delay equal to the heat up time of the wire. In this way those pulses which are delivered through gate 12 ;; to the pulse counter during this heat up time are eliminated.
When measuring veIocity in intermittent flow systems it is o~ten necessary to delay the injection of a thermopulse for a substantial time after the indi-cation of flow if the measurement is to reflect steady state flowconditions. At flow rates of between 20 and 1000 cm3/minute the time for the restoration of a substantially stable flow pattern is between about 0.01 and 0.5 seconds and at flow rates of between 50 and 200 cm3/minute the time is between about 0.05 and 0.2 seconds.
.~j LeA 16,529-Ca -17-~ ~J~
Claims (37)
1. A method for dosing multicomponent liquid systems into a mixing chamber in which the components are conveyed through separate pipes to the mixing chamber, wherein in at least one of the pipes, at a first point in the pipe a heat impulse is produced in the liquid flowing in the pipe, at one or more other points in the pipe downstream of the first point the ascending flank of the heat impulse is detected and the time taken for the heat impulse to reach at least one of the other points is measured, the measured transit time is con-verted into a voltage which is proportional to the flowrate of the liquid in said pipe and the flowrate in the other pipes is controlled proportionally to the voltage.
2. A method according to Claim 1, wherein the transit time is measured taken for the heat impulse to travel the distance between the first point where the heat impulse is produced and a second point, where the heat impulse is detected.
3. A method according to Claim 1, wherein the transit time taken for the heat impulse for travelling the distance between at least two other consecutive points is measured.
4. A method according to Claim 2 or 3, wherein the components are intermittently conveyed and the heat impulse is injected substantially at each moment of restoring the flow of the components.
5. A method according to Claim 3, wherein the transit time is measured successively between more than two consecutive other points.
6. A method according to Claim 2, wherein the transit time is determined by measuring the time lag at the moment where the ascending or descending flank of the heat impulse appears at the first point and the moment where the ascending flank of the heat impulse arrives at the second point.
7. A method according to Claim 3, wherein the transit time is determined by measuring the time lag at the moment where the ascending flank of the heat impulse appears at one of the other points and the moment where this ascending flank arrives at a consecutive other point.
8. A method according to Claim 1, wherein the transit time measurement is effected periodically.
9. A method according to Claim 8, wherein the instantaneous flowrate obtained from a measurement of transit time of an individual heat impulse, is electrically stored until the measurement of transit time is effected with the following heat impulse.
10. A method according to Claims 2 or 3, wherein the components are intermittently conveyed, storing electrically the value of the last measured flowrate and controlling the flowrate in the other pipes in the following period of con-veyance with this measurement result until a subsequent measurement of flowrate is taken.
11. A method according to Claim 1, wherein the transit time is digitally measured in at least one pipe by supplying impulses at a constant pulse frequency to an impulse counter for the period, where the heat impulse travels from the first point to one of the other points or the distance between two successive other points, converting digitally the counter content into a quantity in the binary code which is pro-portional to the flowrate and reconverting this quantity into an analogous signal for actuating control means in the other pipes.
12. The method of Claim 1, wherein the system is two component and wherein the transit time is measured in one pipe and the flowrate in the other pipe is adjusted accordingly.
13. A method according to Claim 8, wherein the detection of a heat impulse at one of the other points triggers a new heat impulse at the first point and the resulting impulse frequency is used as a measure of the flowrate.
14. A method according to Claim 1, wherein the impulse duration is from 5 to 100 ms.
15. A method as claimed in Claim 1, when used for the production of the polyurethane reaction mixtures.
16. An apparatus for carrying out the method of Claim 1, comprising a mixing chamber, a plurality of pipes connected to the mixing chamber, in at least all but one of which is arranged an electrically activated dosing device, a heating wire arranged in at least one of the pipes and down-stream of the heating wire a thermoelectric heat sensor, the heat sensor being electrically connected to an amplifier and a voltage comparator, means for producing periodic heat impulses by passing a current through the heating wire, an electric pulse generator supplying pulses into a counter during the transit time where a heat impulse travels from the heating wire to the thermoelectric sensor, a storing unit for storing the counter content until the next following heat impulse reaches the thermoelectric sensor, a code converter for converting the counter content into a quantity in the binary code which is proportional to the flowrate, a digital-analog converter for reconverting this quantity into an analogous signal and amplifier means for amplifying the analogous signal, being connected to electrically activated dosing devices in the other pipes, the dosing rate of which is proportional to the voltage applied.
17. An apparatus according to Claim 16, comprising a heating wire having a weight of less than 15 mg and means for periodically discharging a condensor through the heating wire within a few milliseconds.
18. An apparatus according to Claim 16, wherein the heat sensor is a differential thermocouple.
19. An apparatus according to Claim 16, wherein the code converter is programmed to yield a quantity which is proportional to the flowrate, when the reciprocal of the flowrate and the transit time are correlated by a non-linear function.
20. An apparatus according to Claim 16, wherein the dosing device comprises a pressure pump.
21. An apparatus according to Claim 16, wherein the dosing device comprises an electrically activated regulating valve.
22. An apparatus according to Claim 16, wherein the distance between the heating wire and the thermoelectric heat sensor is from 5 to 500 mm.
23. A method for dosing multicomponent liquid systems having chemically reactive components, in which the components are conveyed by separate conduits into a mixing chamber, characterized in that a thermopulse is injected in the stream of at least one of said conduits and the transit time of the resulting heat plug is digitally measured by detecting the ascending flank of the thermopulse, the measured transit time is stored and converted by a code-converter into a voltage proportional to the flowrate in said conduit and the flowrates in the other conduits are controlled proportional to this voltage.
24. An apparatus for carrying out the method accord-ing to Claim 1, comprising a mixing chamber with feed conduits, at least all but one of which are provided with dosing devices, characterized in that at least one of the conduits to the mixing chamber is provided with a transit time measuring unit to determine the flowrate, said conduit being the dosing device free conduit if any conduit is dosing device free comprising a heater which is centrally mounted in the conduit and downstream in this conduit a thermoelectric sensor, being connected via an amplifier and a comparator with the reset input of a bistable multivibrator, the multivibrator activating during its set time a gate for the transit time of the heat plug to receive pulses from an impulse generator and the counted pulses in a counter are summed up and stored in a digital counter which is connected to an electronic code-converter and D/A-converter, which produces an electric signal proportional to the flowrate said signal being amplified in a power amplifier and the power ampli-fier being connected to an electrically activated dosing device in each other conduit, the dosing rate of which is proportional to the applied voltage.
25. An apparatus for carrying out the process of Claim 1 comprising:
a) a mixing chamber with feed conduits, at least all but one of which are provided with dosing devices, b) a transit time measuring unit comprising 1) a heater which is centrally mounted in the conduit which may not contain a dosing device and is connected to a power source, 2) a thermoelectric sensor mounted in said conduit between said heater and the mixing chamber, and connected to an amplifier which is connected to a comparator, 3) a bistable multivibrator whose set input is connected to said heater power source and whose reset input is connected to said comparator, 4) a gate connected to said multivibrator so as to pass pulses from a pulse generator to an impulse counter only when said multivibrator is in its set mode, 5) a digital store connected to said counter which stores the sums in said counter and connected to said digital store, c) a control means comprising 1) an electronic code converter and a digital analogue converter which in combination convert said stored value into an electric signal which is proportional to the flow rate of a liquid medium in said conduit, 2) a power amplifier which is adapted to amplify said electric signal and is connected to 3) a control means in each dosing device which controls the dosing rate proportion-al to the signal received from said power amplifier.
a) a mixing chamber with feed conduits, at least all but one of which are provided with dosing devices, b) a transit time measuring unit comprising 1) a heater which is centrally mounted in the conduit which may not contain a dosing device and is connected to a power source, 2) a thermoelectric sensor mounted in said conduit between said heater and the mixing chamber, and connected to an amplifier which is connected to a comparator, 3) a bistable multivibrator whose set input is connected to said heater power source and whose reset input is connected to said comparator, 4) a gate connected to said multivibrator so as to pass pulses from a pulse generator to an impulse counter only when said multivibrator is in its set mode, 5) a digital store connected to said counter which stores the sums in said counter and connected to said digital store, c) a control means comprising 1) an electronic code converter and a digital analogue converter which in combination convert said stored value into an electric signal which is proportional to the flow rate of a liquid medium in said conduit, 2) a power amplifier which is adapted to amplify said electric signal and is connected to 3) a control means in each dosing device which controls the dosing rate proportion-al to the signal received from said power amplifier.
26. An apparatus for carrying out the process of Claim 1 comprising:
a) a mixing chamber with feed conduits, at least all but one of which are provided with dosing devices, b) a transit time measuring unit comprising 1) a heater which is centrally mounted in the optionally dosing device free conduit and is connected to a power source, 2) a thermoelectric sensor mounted in said conduit between said heater and the mixing chamber and connected to 3) an amplifier which connected to 4) a comparator, 5) a bistable multivibrator whose set input is connected to said heater power source and whose reset is connected to said comparator, 6) a gate connected to said multivibrator so as to pass pulses from a pulse generator to an impulse counter only when said multivibrator is in a set mode, 7) a digital store which retains the sum accumulated in said impulse counter from one set reset cycle of said multi-vibrator until the next cycle is completed, and 8) an electronic code converter which converts the sum in the digital store into a quantity directly proportional to the flowrate of a liquid medium in said conduit, and c) a control means comprising 1) a digital analogue converter which converts said quantity into an electrical signal, 2) a power amplifier which amplifies this signal, and 3) a control means in each dosing device which controls the dosing rate pro-portional to said signal.
a) a mixing chamber with feed conduits, at least all but one of which are provided with dosing devices, b) a transit time measuring unit comprising 1) a heater which is centrally mounted in the optionally dosing device free conduit and is connected to a power source, 2) a thermoelectric sensor mounted in said conduit between said heater and the mixing chamber and connected to 3) an amplifier which connected to 4) a comparator, 5) a bistable multivibrator whose set input is connected to said heater power source and whose reset is connected to said comparator, 6) a gate connected to said multivibrator so as to pass pulses from a pulse generator to an impulse counter only when said multivibrator is in a set mode, 7) a digital store which retains the sum accumulated in said impulse counter from one set reset cycle of said multi-vibrator until the next cycle is completed, and 8) an electronic code converter which converts the sum in the digital store into a quantity directly proportional to the flowrate of a liquid medium in said conduit, and c) a control means comprising 1) a digital analogue converter which converts said quantity into an electrical signal, 2) a power amplifier which amplifies this signal, and 3) a control means in each dosing device which controls the dosing rate pro-portional to said signal.
27. A method for dosing multicomponent liquid systems into a mixing chamber in which the components are conveyed through separate pipes to the mixing chamber, wherein in at least one of the pipes, at a first point in the pipe a heat impulse is produced in the liquid flowing in the pipe, at one or more other points in the pipe downstream of the first point the ascending flank of the heat impulse is detected and the time taken for the heat impulse to reach at least one of the other points is measured, the measured transit time is converted into a voltage which is proportional to the flow-rate of the liquid in said pipe and the flowrate in the other pipes is controlled proportionally to the voltage, and wherein the components are intermittently conveyed, the value of the last measured flowrate is stored electrically and the flowrates in the other pipes in the following period of conveyance are controlled with this measurement result until a subsequent measurement of flowrate is taken.
28. A method for measuring the velocity of a liquid flowing continuously or discontinuously in a conduit at rates between about 20 and 1000 cm3/minute comprising (A) injecting a thermopulse of between about 5 and 100 ms in duration into the liquid by means of a wire having a weight of less than about 15 mg and being heated by the discharge of a condensor centrally mounted in the conduit carrying said liquid, (B) simultaneously adjusting a bistable multi-vibrator to its set mode so that it allows pulses from a pulse generator to pass through a gate to a pulse counter, (C) activating said pulse generator for at least one measurement cycle, (D) detecting the arrival of the ascending flank of said pulse with a differential thermocouple mounted in said conduit between about 5 and 500 mm downstream of said heater, (E) amplifying the detection signal of said sensor and passing it to a comparator, (F) using said amplifier signal to activate said comparator and using the output of said comparator to activate the reset mode of said bistable multivibrator thereby closing said gate to further pulses of said pulse generator, (G) converting the value accumulated in said pulse counter during the set/reset cycle of the multi-vibrator to a value equivalent to the velocity of said liquid by means of a permanently programmed ROM-code converter, and (H) storing the value accumulated in said impulse counter until the next set/reset cycle of the multi-vibrator is completed.
29. The method of Claim 28 wherein said liquid flows intermittently and said thermopulse is injected after a time delay from the start of flow sufficient to allow the flow pattern to become stabilized.
30. The method of Claim 28 wherein the flowing liquid has a viscosity of between about 50 and 2000 cP
and a flow rate of between about 50 and 200 cm3/minute.
and a flow rate of between about 50 and 200 cm3/minute.
31. A method for measuring the streaming velocity of an intermittently flowing liquid in a conduit comprising (A) injecting a thermopulse into said streaming liquid after a time delay from the start of flow suffi-cient to allow the flow pattern to become stabilized, (B) digitally measuring the transit time of the resultant heat plug over some measuring distance wherein the ascending flank of said heat plug is used to detect its arrival at the downstream terminus of said measuring distance, and (C) converting said transit time into a value directly proportional to the velocity of said liquid.
32. A method for measuring the streaming velocity of a flowing liquid in a conduit comprising (A) injecting a thermopulse into said streaming liquid, (B) digitally measuring the transit time of the resultant heat plug over some measuring distance wherein the ascending flank of said heat plug is used to detect its arrival at the downstream terminus of said measuring distance, and (C) converting said transit time into a value directly proportional to the velocity of said liquid.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
33. A method for dosing multicomponent liquid systems into a mixing chamber in which the components are conveyed through separate pipes to the mixing chamber, wherein at least one of the pipes, at a first point in the pipe a heat impulse is produced in the liquid flowing in the pipe, at one or more other points in the pipe downstream of the first point the ascending flank of the heat impulse is detected and the time taken for the heat impulse to reach at least one of the other points is measured, said time measurement being adjusted so as not to include the heat up time of the heat impulse means, measured transit time is converted into a voltage which is proportional to the flowrate of the liquid in said pipe and the flowrate in the other pipes is controlled proportionally to the voltage.
34. A method for dosing multicomponent liquid systems into a mixing chamber wherein the components are not continuously conveyed and wherein the components are conveyed in separate pipes at flow rates between about 20 and 1000 cm3/minute comprising:
a) injecting a heat impulse into the liquid flowing in at least one of said pipes after a delay of between about 0.01 and 0.5 seconds from the initiation of flow, said delay being sufficient to ensure that a stable flow pattern has been established, b) digitally determining the transit time of said heat impulse over some distance by detecting the arrival of the ascending flank of said heat impulse at at least one point downstream of the point of injection, c) converting this transit time measurement into the flowrate of the liquid by means of a code-con-verter, d) electrically storing this flowrate value until a subsequent measurement of flowrate is completed, and e) using this value to control the flowrate in the other pipes until a subsequent value is available.
a) injecting a heat impulse into the liquid flowing in at least one of said pipes after a delay of between about 0.01 and 0.5 seconds from the initiation of flow, said delay being sufficient to ensure that a stable flow pattern has been established, b) digitally determining the transit time of said heat impulse over some distance by detecting the arrival of the ascending flank of said heat impulse at at least one point downstream of the point of injection, c) converting this transit time measurement into the flowrate of the liquid by means of a code-con-verter, d) electrically storing this flowrate value until a subsequent measurement of flowrate is completed, and e) using this value to control the flowrate in the other pipes until a subsequent value is available.
35. A method for dosing multicomponent liquid systems into a mixing chamber wherein the components are not continuously conveyed and wherein the components are conveyed in separate pipes at flow rates between about 50 and 200 cm3/minute comprising:
a) injecting a heat impulse into the liquid flowing in at least one of said pipes after a delay of between about 0.05 and 0.2 seconds from the initiation of flow, said delay being sufficient to ensure that a stable flow pattern has been established, b) digitally determining the transit time of said heat impulse over some distance by detecting the arrival of the ascending flank of said heat impulse at at least one point downstream of the point of injection, c) converting this transit time measurement into the flowrate of the liquid by means of a code-converter, d) electrically storing this flowrate value until a subsequent measurement of flowrate is completed, and e) using this value to control the flowrate in the other pipes until a subsequent value is available.
a) injecting a heat impulse into the liquid flowing in at least one of said pipes after a delay of between about 0.05 and 0.2 seconds from the initiation of flow, said delay being sufficient to ensure that a stable flow pattern has been established, b) digitally determining the transit time of said heat impulse over some distance by detecting the arrival of the ascending flank of said heat impulse at at least one point downstream of the point of injection, c) converting this transit time measurement into the flowrate of the liquid by means of a code-converter, d) electrically storing this flowrate value until a subsequent measurement of flowrate is completed, and e) using this value to control the flowrate in the other pipes until a subsequent value is available.
36. A method for measuring the velocity of a liquid flowing continuously or discontinuously in a conduit at rates between about 20 and 1000 cm3/minute comprising (A) injecting a thermopulse of between about 5 and 100 ms in duration into the liquid by means of a heater mounted in the conduit carrying said liquid, (B) simultaneously adjusting a bistable multi-vibrator to its set mode so that it allows pulses from a pulse generator to pass through a gate to a pulse counter, (C) activating said pulse generator for at least one measurement cycle and setting it to zero after a delay equal to the heat up time of the heater after the initiation of a velocity measurement, (D) detecting the arrival of the ascending flank of said pulse with a differential thermocouple mounted in said conduit between about 5 and 500 mm downstream of said heater, (E) amplifying the detection signal of said sensor and passing it to a comparator, (F) using said amplified signal to activate said comparator and using the output of said comparator to activate the reset mode of said bistable multivibrator thereby closing said gate to further pulses of said pulse generator, (G) converting the value accumulated in said pulse counter during the set/reset cycle of the multivibrator to a value equivalent to the velocity of said liquid by means of a permanently programmed ROM-code converter, and (H) storing the value accumulated in said impulse counter until the next set/reset cycle of the multi-vibrator is completed.
37. A method for measuring the streaming velocity of an intermittently flowing liquid in a conduit compris-ing (A) injecting a thermopulse into said streaming liquid after a time delay from the start of flow suffic-ient to allow the flow pattern to become stabilized, (B) digitally measuring the transit time of the resultant heat plug over some measuring distance wherein the ascending flank of said heat plug is used to detect its arrival at the downstream terminus of said measuring distance and wherein the transit time is adjusted to exclude the heat up time of the means used to inject the thermopulse, and (C) converting said transit time into a value directly proportional to the velocity of said liquid.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19752527378 DE2527378B2 (en) | 1975-06-19 | 1975-06-19 | METHOD AND DEVICE FOR DOSING MULTI-COMPONENT LIQUID SYSTEMS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1075489A true CA1075489A (en) | 1980-04-15 |
Family
ID=5949465
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA254,503A Expired CA1075489A (en) | 1975-06-19 | 1976-06-10 | Measurement and control of multicomponent liquid systems |
Country Status (15)
| Country | Link |
|---|---|
| JP (1) | JPS522761A (en) |
| AT (1) | AT345257B (en) |
| AU (1) | AU505260B2 (en) |
| BE (1) | BE843084A (en) |
| BR (1) | BR7603929A (en) |
| CA (1) | CA1075489A (en) |
| CH (1) | CH622962A5 (en) |
| DE (1) | DE2527378B2 (en) |
| DK (1) | DK274176A (en) |
| ES (1) | ES448994A1 (en) |
| FR (1) | FR2316651A1 (en) |
| GB (1) | GB1548598A (en) |
| IT (1) | IT1060898B (en) |
| NL (1) | NL7606661A (en) |
| SE (1) | SE419680B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2936223A1 (en) * | 1979-09-07 | 1981-03-19 | Bayer Ag, 5090 Leverkusen | METHOD AND DEVICE FOR PRODUCING A REACTION MIXTURE FROM FLOWABLE, FOAM OR SOLID COMPONENTS |
| JPS57120816A (en) * | 1981-01-19 | 1982-07-28 | Anima Kk | Heat ray pulse flowmeter |
| DE3231663C2 (en) * | 1981-01-19 | 1987-09-17 | Anima Corp | Heat pulse type flowmeter - has detector output to vary heating and detection cycle in accordance with flow rate |
| JPS57211015A (en) * | 1981-06-22 | 1982-12-24 | Anima Kk | Heat pulse type thermometer |
| JPS57206830A (en) * | 1981-06-12 | 1982-12-18 | Anima Kk | Heat pulse system flow meter |
| GB2116720B (en) * | 1982-03-08 | 1986-03-12 | Roeh Ind Ltd | Flow rate sensor |
| JPS5978928U (en) * | 1982-11-18 | 1984-05-28 | 澤藤電機株式会社 | Diesel engine fuel flow meter |
| DE3420815A1 (en) * | 1984-05-30 | 1986-05-22 | Andreas Dr. 1000 Berlin Kage | Electronic metering unit for metering extremely small amounts of solvent at high pressure by means of a virtually inertia-less micro-metering valve, a solvent-independent flowmeter system and a low-axial-delay measuring section |
| JPS6074049U (en) * | 1984-06-07 | 1985-05-24 | 株式会社島津製作所 | Gas chromatograph |
| JPS6190765A (en) * | 1984-10-11 | 1986-05-08 | Toyota Motor Corp | Method for detecting abnormal flow rate in multiple liquid painting |
| DE4243573A1 (en) * | 1992-12-22 | 1994-06-23 | Lang Apparatebau Gmbh | Calorimetric flow meter |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3019647A (en) * | 1957-08-30 | 1962-02-06 | Honeywell Regulator Co | Electrical fluid-flow measuring apparatus |
| DE1913544A1 (en) * | 1969-03-18 | 1970-10-01 | Appbau Gauting Gmbh | Measurement method and device for determining the flow speed and flow direction of a medium |
| DE1954835A1 (en) * | 1969-10-31 | 1971-05-13 | Rota App Und Maschb Dr Hennig | Flow meter based on the pulse frequency method |
| DE2151774C3 (en) * | 1971-10-18 | 1980-04-03 | Robert Bosch Gmbh, 7000 Stuttgart | Fuel injection system for an internal combustion engine |
| US3807228A (en) * | 1971-11-02 | 1974-04-30 | Gulf Research Development Co | Ultrasonic velocity and mass flowmeter |
| JPS49106375A (en) * | 1973-02-09 | 1974-10-08 | ||
| GB1459448A (en) * | 1973-02-27 | 1976-12-22 | Nat Res Dev | Inhibition circuits for anemometers |
-
1975
- 1975-06-19 DE DE19752527378 patent/DE2527378B2/en not_active Ceased
-
1976
- 1976-06-10 CA CA254,503A patent/CA1075489A/en not_active Expired
- 1976-06-16 IT IT24406/76A patent/IT1060898B/en active
- 1976-06-16 AT AT442576A patent/AT345257B/en not_active IP Right Cessation
- 1976-06-16 CH CH769976A patent/CH622962A5/de not_active IP Right Cessation
- 1976-06-16 AU AU14943/76A patent/AU505260B2/en not_active Expired
- 1976-06-17 SE SE7606933A patent/SE419680B/en unknown
- 1976-06-18 ES ES448994A patent/ES448994A1/en not_active Expired
- 1976-06-18 NL NL7606661A patent/NL7606661A/en not_active Application Discontinuation
- 1976-06-18 BR BR7603929A patent/BR7603929A/en unknown
- 1976-06-18 GB GB25291/76A patent/GB1548598A/en not_active Expired
- 1976-06-18 DK DK274176A patent/DK274176A/en unknown
- 1976-06-18 FR FR7618682A patent/FR2316651A1/en active Granted
- 1976-06-18 BE BE2055120A patent/BE843084A/en unknown
- 1976-06-18 JP JP51071268A patent/JPS522761A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| AT345257B (en) | 1978-09-11 |
| BE843084A (en) | 1976-12-20 |
| DE2527378B2 (en) | 1977-07-14 |
| NL7606661A (en) | 1976-12-21 |
| DK274176A (en) | 1976-12-20 |
| DE2527378A1 (en) | 1976-12-23 |
| ATA442576A (en) | 1978-01-15 |
| ES448994A1 (en) | 1977-07-01 |
| GB1548598A (en) | 1979-07-18 |
| IT1060898B (en) | 1982-09-30 |
| FR2316651B1 (en) | 1982-11-19 |
| JPS612967B2 (en) | 1986-01-29 |
| FR2316651A1 (en) | 1977-01-28 |
| BR7603929A (en) | 1977-04-05 |
| CH622962A5 (en) | 1981-05-15 |
| JPS522761A (en) | 1977-01-10 |
| SE7606933L (en) | 1976-12-20 |
| AU1494376A (en) | 1977-12-22 |
| SE419680B (en) | 1981-08-17 |
| AU505260B2 (en) | 1979-11-15 |
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