WO1992001956A1 - Detecteur de position de feuillard - Google Patents

Detecteur de position de feuillard Download PDF

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Publication number
WO1992001956A1
WO1992001956A1 PCT/AU1991/000320 AU9100320W WO9201956A1 WO 1992001956 A1 WO1992001956 A1 WO 1992001956A1 AU 9100320 W AU9100320 W AU 9100320W WO 9201956 A1 WO9201956 A1 WO 9201956A1
Authority
WO
WIPO (PCT)
Prior art keywords
coils
pair
primary
secondary coils
strip
Prior art date
Application number
PCT/AU1991/000320
Other languages
English (en)
Inventor
Bruce Robert Morrison
Original Assignee
John Lysaght (Australia) Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by John Lysaght (Australia) Limited filed Critical John Lysaght (Australia) Limited
Priority to AU82844/91A priority Critical patent/AU663849B2/en
Publication of WO1992001956A1 publication Critical patent/WO1992001956A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils
    • G01V3/104—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils
    • G01V3/105—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops

Definitions

  • the present invention is directed to sensors for detecting the position of a metal strip and to apparatus incorporating such sensors for monitoring the position of the pass line of the strip.
  • Conventional strip position monitors use optical or electronic sensors to produce a signal indicative of the strip's position relative to the sensor, and outputting means responsive to that signal which display, record or control the position of the strip.
  • optical sensors may be unusable in extremely dusty conditions, and electronic sensors in high temperature conditions. Therefore it is an object of the present invention to provide a strip position sensor able to function satisfactorily in harsh environments such as those instanced above.
  • the invention was devised primarily to monitor the pass line of a steel strip in a continuous hot dip coating process, that is to say a process wherein the strip is passed through a pool of molten coating metal, typically zinc or a mixture of aluminium and zinc, to acquire a liquid coating, which thereafter solidifies on the strip. More specifically, the invention was devised to monitor the pass line as the strip leaves the pool, to enable adjustment of a conventional, gas stripping nozzle assembly, whereby gas jets are directed against each side of the strip to remove surplus liquid coating metal from the strip before it solidifies.
  • molten coating metal typically zinc or a mixture of aluminium and zinc
  • a hood prevents the operator from observing whether the strip is in the centre of the gap between the nozzles of the assembly, as needed to equalise the coating thickness on each side of the strip.
  • a window in the hood There is no point in providing a window in the hood as it soon becomes opaque due to the deposition of a dust of solidified droplets of the coating material.
  • the dust precludes the use of optical sensors within the hood, and the temperature militates against the use of sensors containing electronic components close to the strip, be it within or without a hood.
  • sensors according to the invention are able to operate in the hostile environment within such a hood, where more conventional known sensors are precluded, but it will be appreciated that they may be used with advantage in other, maybe less hostile, environments.
  • the invention consists in a metal strip position sensor comprising a pair of substantially co-axial, spaced apart, primary coils connected in series, a pair of substantially co-axial, spaced apart secondary coils respectively associated with the primary coils and disposed with each secondary coil in field linkable relationship with its associated primary coil, and mounting means supporting said coils, with one primary coil and its associated secondary coil on one side of a desired centre plane of a metal strip to be monitored and the other primary coil and its associated secondary coil on the other side of said centre plane, and enabling such a strip, to pass freely between the coils on each side thereof.
  • each secondary coil is preferably closely adjacent its associated primary coil.
  • the sensor of the invention may be utilised as the sensor in a strip position monitor further comprising energising means to apply a substantially constant alternating voltage of predetermined frequency across said primary coils to produce an alternating primary magnetic field, and voltage responsive means responsive to the voltages generated in the secondary coils to indicate and/or control the deviation of such a metal strip from said plane in the vicinity of said secondary coils.
  • those voltage responsive means comprise comparator means generating a signal indicative of the relationship between the voltages generated in the respective secondary coils and outputting means responsive to that signal for displaying or controlling the strip deviation.
  • the voltage responsive means comprise comparator means and outputting means there may be a comparator means for each pair of secondary coils and a single outputting means able to be switched from one comparator means to another as desired.
  • a monitor according to the invention which requires to be close to the monitored strip is the characterising sensor.
  • the characterising sensor comprises simple passive coils it may be readily designed to be capable of withstanding hostile environments.
  • the principle of operation of the sensor is that the primary coils create a magnetic field pattern which is disturbed by changes in the position of the strip. Notwithstanding such disturbances the total magnetic flux linking the primary coils is constant, because they are in series and the voltage across them is constant, thus any change in the field pattern necessarily alters the proportion of the total flux linking them individually, and thus the fluxes linking their respectively associated secondary coils. Therefore the voltages generated in the secondaries are not only dependent on the position of the strip but also will display a unique relationship for each and every position of the strip.
  • the strip acts as a magnetic shunt attracting magnetic flux, thereby increasing the flux through the secondary coil it is closer to and decreasing the flux through the secondary coil it is further from.
  • the strip is ferrous and the frequency is more than about 6 kHz, eddy currents induced in the strip repel the field and the strip acts as a flux barrier, thereby decreasing the flux through the secondary coil it is nearer to and increasing the flux through the secondary coil it is further from.
  • the strip is non-ferrous and the frequency very much higher still, say 50 kHz or more, depending largely on the resistivity of the strip material, the effect is similar to the last mentioned effect for a ferrous strip.
  • the magnetic axes of all the coils are substantially perpendicular to the desired centre plane
  • the secondary coils are fairly tightly coupled to the primary coils
  • the coil arrangement is symmetrical about the centre plane (that is to say the coils on one side of the centre plane are a mirror image of those on the other)
  • the primary coils are mutually aiding
  • the secondary coils are mutually opposing.
  • the induced secondary voltages are substantially equal when the strip is centred between the coils, but become unbalanced in one or the other direction as the strip moves away from centre.
  • the comparator means may respond to the relative magnitudes of the individual secondary voltages.
  • the secondary coils are connected in series, to produce a differential output signal, that is to say a signal equal to the difference between their induced voltages, and that signal is fed to comparator means preferably comprising a phase sensitive rectifier deriving its reference voltage directly from the energising means.
  • comparator means preferably comprising a phase sensitive rectifier deriving its reference voltage directly from the energising means.
  • the output of the rectifier is a DC signal with amplitude proportional to the deviation of the strip from the central position. Deviations in one direction give positive DC signals, and deviations in the other direction give negative DC signals.
  • the output signal of the rectifier has a very low noise level, and may be fed directly to a DC voltmeter calibrated to indicate the position of the strip to an accuracy of 0.5 mm or better.
  • Figure 1 is a schematic plan view of a sensor according to the invention in place in relation to a strip to be monitored.
  • Figure 2 is a schematic sectional view taken on line 2-2 of figure 1 drawn to a larger scale.
  • Figure 3 is a schematic diagram of the sensor of figure 1.
  • Figure 4 is a block diagram of a strip position monitor incorporating the sensor of figures 1 , 2 and 3.
  • the sensor illustrated by figures 1 , 2 and 3 comprises a pair of elongated primary coils 8 and seven pairs of independently operating secondary coils 1 to 7.
  • the primary coils 8 are wound in the same direction when viewed along the axis of the pair and are connected in series. They are supported by non-metallic formers 9 able to withstand temperatures of the order of 250°C and held by mounting means (not shown in detail but including the formers 9 and spacers 10) on opposite sides of a steel strip 11 , which may be emerging from a galvanising bath.
  • Those mounting means are themselves then mounted on the gas stripping nozzle assembly whereby the thickness of the zinc coating is controlled.
  • the arrangement is such that when the strip 11 is centrally positioned between the coils 8 then it is likewise centrally positioned between the nozzles of that assembly.
  • the formers 9, and thus the primary coils 8 are appreciably longer than the width of the strip 11. This is to eliminate edge effects and ensure when the primary coils are energised that each pair of secondary coils 1 to 7 respectively is operating under substantially identical conditions insofar as the total primary field linkage with them is concerned.
  • the individual secondary coils of each pair are wound on paired formers 12.
  • the pairs of secondary coil formers are spaced apart laterally so that each pair of secondary coils links a discrete part of the primary field, not linked by any other pair.
  • the secondary coils of each pair are wound in opposite directions, when viewed along the axis of the pair, and are also connected in series, so that the output from each pair is the difference between the voltages induced in the individual coils of that pair. .
  • the primary coils 8 of a sensor 13 according to figures 1 to 3 are energised by a power amplifier 14 fed by a function generator 15.
  • the function generator may be a commercially available unit which nominally produces a sine wave signal of 0.5 V rms and an in phase square wave signal of +/- 2V.
  • the sine wave signal is fed to the power amplifier 14 and the square wave signal is fed, as a reference signal, to each of seven phase sensitive rectifiers 16, only one of which appears in the diagram, although in practice there is preferably one for each of the seven pairs of secondary coils.
  • a single rectifier may be switched from pair to pair of secondary coils as required.
  • a frequency is effective to generate eddy currents in the steel strip, but has little effect on zinc or other non- ferrous accretions which would otherwise produce spurious results.
  • a frequency is chosen which is also sufficiently far from the frequencies used in induction heaters to permit ready suppression of any untoward interference that might otherwise arise if such heaters should be operating nearby, also care should be taken to avoid the harmonics and sub-harmonics of magnetic influences of same.
  • the amplifier 14 may be a commercially available unit with a nominal output of 25 V 0-pk.
  • the primary coils 8 may be spaced apart by about 150 mm. They may each have 10 turns and the secondary coils 1 to 7 may each have 100 turns.
  • each pair of secondary coils 1 to 7 which in this instance may amount to a maximum of about 1 V 0-pk, is fed to an associated phase sensitive rectifier 16, which also receives a reference voltage from the generator 15.
  • the positive or negative DC signals from the phase sensitive rectifier which may range from -5 V to +5 V dc may be displayed by outputting means such as a cathode ray oscilloscope or a simple voltmeter. In some instances they may constitute the error signal of a servo-mechanism effecting automatic positional adjustment of a related component or the like.
  • Each pair of secondary coils 1 to 7 provides an output related to the position of the strip in the locality of the pair.
  • each pair feeds its own related comparator means the several indications may indicate lack of flatness in the strip, for example "gutter” and other related phenomena.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Electromagnetism (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

Détecteur (13) destiné à être utilisé dans un dispositif de surveillance de la position d'une bande de métal, servant à déterminer la position de la ligne de passe optimale d'un feuillard d'acier (11) sortant d'un bain de galvanisation et passant dans une cloche située au-dessus, le détecteur (13) étant capable de supporter les conditions existant à l'intérieur de la cloche. Le détecteur comprend une paire de bobines primaires (8) allongées pratiquement coaxiales, espacées l'une de l'autre en série, une pluralité de paires de bobines secondaires espacées latéralement (1..7) pratiquement coaxiales et espacées, placées entre les bobines primaires (8) et couplées respectivement à ces dernières (8), et un dispositif de montage (9, 10, 12) maintenant toutes lesdites bobines (8, 1..7) dans une relation fixe, avec une bobine primaire et une bobine secondaire de chaque paire se trouvant d'un côté de la ligne de laminage optimale désirée du feuillard (11) alors que l'autre bobine primaire et l'autre bobine secondaire de chaque paire se trouvent de l'autre côté de ladite ligne de laminage optimale. L'invention concerne également un dispositif de surveillance utilisant le détecteur (13), dans lequel les bobines secondaires de chaque paire sont reliées en série en opposition et qui comprend également un générateur de fonctions (15) et un amplificateur de puissance (14) qui excite les bobines primaires (8) du détecteur à une fréquence de 9,7 kHz, et sept redresseurs (16) sensibles à la phase qui s'associent respectivement aux paires de bobines secondaires. Chaque redresseur est alimenté avec une tension de référence rectangulaire à 9,7 kHz provenant directement du générateur de fonctions (15) et avec la sortie provenant de sa paire associée de bobines secondaires afin de produire un signal à courant continu qui indique la position du feuillard au voisinage de la paire associée de bobine secondaires.
PCT/AU1991/000320 1990-07-20 1991-07-18 Detecteur de position de feuillard WO1992001956A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU82844/91A AU663849B2 (en) 1990-07-20 1991-07-18 Strip position sensor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPK1279 1990-07-20
AUPK127990 1990-07-20

Publications (1)

Publication Number Publication Date
WO1992001956A1 true WO1992001956A1 (fr) 1992-02-06

Family

ID=3774838

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1991/000320 WO1992001956A1 (fr) 1990-07-20 1991-07-18 Detecteur de position de feuillard

Country Status (1)

Country Link
WO (1) WO1992001956A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4126921A1 (de) * 1991-08-14 1993-02-18 Elmeg Verfahren und vorrichtung zur induktiven messung der lage eines metallbandes

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1219480A (en) * 1967-04-10 1971-01-13 Outokumpu Oy Method and device for detecting the presence of electrically conductive bodies
GB1418476A (en) * 1972-10-17 1975-12-24 Frankel Aluminium Ltd J Detection of ferromagnetic materials
US3950696A (en) * 1974-04-29 1976-04-13 Westinghouse Electric Corporation Trapezoidal coil configuration for metal detector in the shape of an inverted u
GB1436900A (en) * 1972-05-26 1976-05-26 Heytow S Metal detector
GB1570640A (en) * 1977-02-01 1980-07-02 Imi Kynoch Ltd Magnetic detector
GB1585301A (en) * 1976-08-18 1981-02-25 Knogo Corp Method and apparatus for detecting the presence of an article in an interrogation zone
GB2110825A (en) * 1981-11-06 1983-06-22 Outokumpu Oy Apparatus for detecting metal objects
EP0096568A1 (fr) * 1982-06-09 1983-12-21 Deere & Company Système de détection de métal
DE3731329A1 (de) * 1987-02-03 1988-08-18 Giovanni Manneschi Metalldetektor
US4779048A (en) * 1985-11-02 1988-10-18 Vallon Gmbh Metal detector for detecting metal objects

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1219480A (en) * 1967-04-10 1971-01-13 Outokumpu Oy Method and device for detecting the presence of electrically conductive bodies
GB1436900A (en) * 1972-05-26 1976-05-26 Heytow S Metal detector
GB1418476A (en) * 1972-10-17 1975-12-24 Frankel Aluminium Ltd J Detection of ferromagnetic materials
US3950696A (en) * 1974-04-29 1976-04-13 Westinghouse Electric Corporation Trapezoidal coil configuration for metal detector in the shape of an inverted u
GB1585301A (en) * 1976-08-18 1981-02-25 Knogo Corp Method and apparatus for detecting the presence of an article in an interrogation zone
GB1570640A (en) * 1977-02-01 1980-07-02 Imi Kynoch Ltd Magnetic detector
GB2110825A (en) * 1981-11-06 1983-06-22 Outokumpu Oy Apparatus for detecting metal objects
EP0096568A1 (fr) * 1982-06-09 1983-12-21 Deere & Company Système de détection de métal
US4779048A (en) * 1985-11-02 1988-10-18 Vallon Gmbh Metal detector for detecting metal objects
DE3731329A1 (de) * 1987-02-03 1988-08-18 Giovanni Manneschi Metalldetektor

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4126921A1 (de) * 1991-08-14 1993-02-18 Elmeg Verfahren und vorrichtung zur induktiven messung der lage eines metallbandes
EP0529440A1 (fr) * 1991-08-14 1993-03-03 Elektro-Mechanik Gmbh Appareil de mesure de la position d'une tôle métallique au moyen inductif
US5339029A (en) * 1991-08-14 1994-08-16 Elecktro-Mechanik Gmbh Methods and apparatus for measuring the postion of an edge of a metal strip by electronic induction

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