CA1122669A - Magnetic detector - Google Patents
Magnetic detectorInfo
- Publication number
- CA1122669A CA1122669A CA296,268A CA296268A CA1122669A CA 1122669 A CA1122669 A CA 1122669A CA 296268 A CA296268 A CA 296268A CA 1122669 A CA1122669 A CA 1122669A
- Authority
- CA
- Canada
- Prior art keywords
- detector
- ferromagnetic material
- ferromagnetic
- search
- field
- 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
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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
- G01V3/107—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 using compensating coil or loop arrangements
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- 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)
- Geophysics And Detection Of Objects (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention provides a magnetic scrap sorter for detecting ferromagnetics in a mass of basically non-ferromagnetic material. The apparatus includes a magnetic search coil located within a magnetic field having a sub-stantially constant level with means to respond to signals generated by the search coil resulting from ferromagnetics passing through the search area of the search coil. The method has particular application to the detection of ferro-magnetic impurities in titanium scrap.
The invention provides a magnetic scrap sorter for detecting ferromagnetics in a mass of basically non-ferromagnetic material. The apparatus includes a magnetic search coil located within a magnetic field having a sub-stantially constant level with means to respond to signals generated by the search coil resulting from ferromagnetics passing through the search area of the search coil. The method has particular application to the detection of ferro-magnetic impurities in titanium scrap.
Description
llZ2~i69 This invention relates to the detection of ferromagnetic material, in a background of paramagnetic material of metallic or non-metallic character and has particular but not exclusive relevance to the detection of ferromagnetic impurities in titanium scrap.
The use of titanium scrap as a source of secondary material is subject to a number of constraint. For applications where extremely high integrity of the product is required such as in aeroengine components it is essential that the secondary material be completely examined to extract impurities. The impurities which cause most problems are those which come from the machining of titanium and in particular the tool tips used in machining can break off and fall into the titanium swarf. These tool tips are extremely dense and hard and are often not completely broken down by the subsequent mclting. They are there-fore a potential source of mechanical failure in the final product. So far as is known there has been no method of automatically detecting ferromagnetic mater-- ials in a non-magnetic matrix such as titanium swarf which gives sufficiently reliable operation to enable it to be relied upon.
By the present invention there is provided a method of detecting particles of tool tips containing a ferromagnetic material in a matrix of metallic non-ferromagnetic material which comprises the steps of passing the matrix through a detector unit, the detector unit comprising magnetic sensor means located within an area of applied magnetic field, the applied magnetic field having a substantially constant zone in which the magnetic sensor means is located, the applied magnetic field being generated by an electromagnet whichis so disposed that the uniform magnetic field has parallel lines of flux in a vertical direction, the matrix material being passed vertically downwardly through the field parallel to the lines of flux in a lamellar manner at least in part under the action of gravity.
The use of titanium scrap as a source of secondary material is subject to a number of constraint. For applications where extremely high integrity of the product is required such as in aeroengine components it is essential that the secondary material be completely examined to extract impurities. The impurities which cause most problems are those which come from the machining of titanium and in particular the tool tips used in machining can break off and fall into the titanium swarf. These tool tips are extremely dense and hard and are often not completely broken down by the subsequent mclting. They are there-fore a potential source of mechanical failure in the final product. So far as is known there has been no method of automatically detecting ferromagnetic mater-- ials in a non-magnetic matrix such as titanium swarf which gives sufficiently reliable operation to enable it to be relied upon.
By the present invention there is provided a method of detecting particles of tool tips containing a ferromagnetic material in a matrix of metallic non-ferromagnetic material which comprises the steps of passing the matrix through a detector unit, the detector unit comprising magnetic sensor means located within an area of applied magnetic field, the applied magnetic field having a substantially constant zone in which the magnetic sensor means is located, the applied magnetic field being generated by an electromagnet whichis so disposed that the uniform magnetic field has parallel lines of flux in a vertical direction, the matrix material being passed vertically downwardly through the field parallel to the lines of flux in a lamellar manner at least in part under the action of gravity.
-2-~.
ilZZ6~9 The coil produces, in use, an electric output signal when ferrogmagnetic material moves past it.
The particulate material may be fed to the detector unit by a travelling wave vibratory feeder the exit end of which may be disposed vertically above the parallel lines of force. The exit end of the vibratory feeder may have a smaller gate size than the cross-sectional size of the parallel lines of a tube through which the material falls. The particulate material may be passed through the magnetic field in a forced air flow which accelerates the particles before passing the particles through the field.
Preferably there are two search coils connected in series opposition so that their response to perturbations in the uniform external field is zero.
The sensor may be of tubular or ring-like formation the material passing through the tubular or rin~-like structure.
There is preferably provided an iron shield around the magnetic sensor and field generating member. Further, there is preferably provided an electrostatic screen within the tubular or ring-like sensor.
~ 20 Preferably, at specified times, a known ferromagnetic -- material or a container cont~ining a known ferromagnetic material is passed through the detector unit to confirm satisfactory operation of the detector unit.
The present invention also provides a detector for detecting ferromagnetic material in a matrix of non-ferromagnetic metallic material which includes a search coil located within an electromagnetic field of substantially constant strength and means to detect in use a voltage generated through the search coil on ;: , .
1122~69 the passage of a ferromagnetic material through the search coil, the field being generated by an electroma~net and having a plurality of parallel lines of flux disposed in a vertical direction, the matrix - 3a -~lZ2~ 9 material being in particulate form and being dropped through the parallel lines of flux in a vertical direction under the action of gravity by a travelling wave vibratory feeder, the exit end of which is disposed vertically above the parallel lines of flux.
There may be two search coils connected in series opposition so that their response to a uniform external field is zero. The search coils may be movable one relative to the other for setting-up purposes whereby the detector may be zeroed by relative movement of the two search coils, the search coils being then fixed relative one to the other during normal operation of the detector. There may be provided further means to remove the ferromagnetic particles from the non-ferromagnetic material after detection thereof.
The removing means may comprise an interrupter to interrupt the flow of material through a passageway to prevent that portion of the material containing the ferromagnetic particles from passing to a receptacle. The interrupter may comprise a plate~
By way of exa~ple only an e~bodiment of the invention will now be described with reference to the accompanying diagrammatic drawings of which:
Figure 1 is a schematic cross-section of a magnet and search coil assembly;
Figure 2 is a schematic cross-section of a detector and separator unit; and Figure 3 is a schematic view of the deflector plate of Figure 2.
E
~122669 A pair of magnetic search coils 1,2 which form a conventional magnetometer is located within the centre of a DC electromagnetic solenoid 3. The solenoid provides a zone, in which the coils 1,2 are located of substantially constant field with the flux lines being disposed parallel to one another and in a vertical direction.
Surrounding the solenoid 3 is an iron shield ~ and an electrostatic screen 5 defines a bore within the iron shield through which passes a tube 6 of dielectric material such as glass. Titanium swarf which may include ferromagnetic lumps passes vertically down through the tube 6 in a lamellar manner in the direction of the arrow 7 under the action of gravity. Any ferromagnetic material in the stream of scrap is magnetised by the solenoid 3 and movement of the magnetised particles through the search coil produces a voltage output from the coil and this can be detected by suitable voltage means not shown.
It is important, when using a titanium swarf that the passage of the particles through the solenoid should be parallel to the lines of force, if the particles were to move across the width of the tube 6 they would cross the parallel lines of flux, and in crossing the flux lines would generate eddy currents which would give rise to a magnetic field which would be picked up by the search coils. This would therefore give a false indication of the presence of a ferromagnetic material, consequently operating in error the rejection mechanism described below. It will be understood, therefore, that when using a conducting matrix it is important to use a method of feeding which provides for the passage of particles through the solenoid in a parallel manner. Particular examples of this method are described below.
~Z2669 The detector means may supply an output signal to any form of suitable indicator such as a meter or light signal. The meter may be connected to means to reject the particle from the stream.
Such a means could be an air jet connected to the detector through a suitable delay circuitry. The electrical circuitry is of a conventional type and is not part of the present invention. The use of two search coils enables the system to be relatively insensitive to externally generated electromagnetic fields. Although a single coil could be used and electronic amplification of the necessary sensitivity is readily available the presence of fluctuating electro-magnetic fields makes it difficult to use this sensitivity in practice.
Referring to Figures 2 and 3 these show a separator unit incorporating the detector of Figure 1. Titanium swarf is passed in the direction of arrow 10 into a feeder trough 11. The feeder trough 11 is a vibratory feeder which works by establishing a travelling wave in material located on the surface of the feeder. Particles on the moving surface of the feeder are moved forwards by the action of the travelling wave and eventually arrive at the exit end of the feeder which is located above a guide tube 12. The particles are simply moved over the end of the exit end without being given a forward component of movement thereby dropping straight down through the guide tube 12. If a conveyor belt, for example, were to be used to move material into the guide tube 12 it would give the particles a forward or translational movement which would not be damped by the guide tube and thus the particles would fall down through the guide tube and would ricochet or bounce off the walls of the guide tube and would set up eddy currents within the search coils.
-' ' : ' . . : .
~lZ266~
An alternative method of passing the particles in a lame]lar manner through the guide tube is to entrain them in a moving air stream such that the particles are accelerated initially to space out the particles and damp translational movement and have them moving in a parallel manner vertically downwards in the region of the search coils 1 and 2.
The exit end of the feeder 11 preferably is smaller than the guide tube 12 so that the particles can fall freely through the guide tube.
The exit end of the feeder is conventionally referred to as the gate and the gate width is preferably less than the cross-sectional size of the tube 12.
This feeder passes the swarf into the guide tube 12 which is arranged vertically to permit the swarf to pass down through the detector unit indicated generally by 13. An inclined plate 14 can act to deflect swarf when in the position illustrated through chute 15 into receptacle 16.
If the inclined plate 14 is not in position the swarf will fall through chute 17 into receptacle 18. The inclined plate is driven as is shown more clearly in Figure 3.
In Figure 3 the plate 14 is movable by means of air-operated cylinders 19,20 to obscure hole 21 which is the extension of tube 12.
Thus as long as plate 14 is in the retracted position as shown in Figure 3 swarf will fall through the tube 12 and tube 17 into receptacle 18.
Upon detection of a ferromagnetic particle cylinders 19 and 20 push plate 14 over aperture 21, deflecting the particles through tube 15 into receptacle 16. Obviously the deflected particles will include non-ferromagnetic material as well as the ferromagnetic material because the response time of the equipment would not be sufficiently accurate only to deflect the ferromagnetic material. This swarf ~1226E;9 can, however, be recycled by periodically removing the contents of receptacle 16 and passing them through the machine again. In order that it can be obvious that the machine is working large plastic balls containing small quantities of ferromagnetic material can be inserted through funnel 21 as shown at 22. These parts will operate the machine and be deflected thereby proving that the machine is functioning and acting as a continuous monitor and indicator. This visual signal can be used to reassure the operators that the machine is working satisfactorily.
With the two search coils mounted inside the magnetising solenoid and being connected in series opposition their response to a change in external field is zero. As the magnetic particles fall consecutively through each coil a voltage pulse in the series circuit is produced as each particle leaves the upper search coil and enters the lower.
If the search coils each enclose the same number of area turns (area of cross-section times the number of turns) and are mounted in the magnetic centre of the magnet the system does not respond the fluctuations in the magnetising current. Fine corrections may be made by slightly moving the two coils within the magnet to the place where the minimum electrical noise is picked up. The iron shield is used because without it the system tends to respond to non-uniform external fields as the fields in each of the search coils may be different.
Electrostatic screening is provided as shown and of course the electrical leads from the search coils to the amplification means should also be screened.
Because the magnetic flux enclosed by the pair of search coils depends on the position of the coils within the solenoid relative motion between the two will also cause electrical noise. It is -- -- --~ , ~122~6~
important therefore that the search coils be rigidly attached to each other and to the solenoid. In addition the central tube down which the particles fall should be separated from the search coils in order that mechanical vibration or electrostatic pick up be reduced.
A version of the invention having a solenoid which produced a field of 0.1 Tesla in a bore of 72mm diameter was tested with search coils each having 67 000 turns at a diameter of 30mm.
Titanium swarf contained in particles of tungsten carbide tool tip of mass 2 x 10~3g was dropped through the central tube. A pulse of 0.2mV and 20ms duration was generated. The background from the uncontaminated titanium swarf was small, being less than 0.02mV.
It will be appreciated that typical tool tip material comprises only 5 to 15% by mass of ferromagnetic material. Consequently, the detector is capable of determining the presence of 0.1mg of material with ferromagnetic susceptibility.
It will be appreciated that the invention is not limited to the detection of ferromagnetic material in titanium swarf. The apparatus may simply be used if necessary after calibration to detect any ferromagnetic material in a non-magnetic matrix, such as food, ie peas, beans, currants etc, or other non-magnetic material such as brass, copper, or wood chips.
;~
ilZZ6~9 The coil produces, in use, an electric output signal when ferrogmagnetic material moves past it.
The particulate material may be fed to the detector unit by a travelling wave vibratory feeder the exit end of which may be disposed vertically above the parallel lines of force. The exit end of the vibratory feeder may have a smaller gate size than the cross-sectional size of the parallel lines of a tube through which the material falls. The particulate material may be passed through the magnetic field in a forced air flow which accelerates the particles before passing the particles through the field.
Preferably there are two search coils connected in series opposition so that their response to perturbations in the uniform external field is zero.
The sensor may be of tubular or ring-like formation the material passing through the tubular or rin~-like structure.
There is preferably provided an iron shield around the magnetic sensor and field generating member. Further, there is preferably provided an electrostatic screen within the tubular or ring-like sensor.
~ 20 Preferably, at specified times, a known ferromagnetic -- material or a container cont~ining a known ferromagnetic material is passed through the detector unit to confirm satisfactory operation of the detector unit.
The present invention also provides a detector for detecting ferromagnetic material in a matrix of non-ferromagnetic metallic material which includes a search coil located within an electromagnetic field of substantially constant strength and means to detect in use a voltage generated through the search coil on ;: , .
1122~69 the passage of a ferromagnetic material through the search coil, the field being generated by an electroma~net and having a plurality of parallel lines of flux disposed in a vertical direction, the matrix - 3a -~lZ2~ 9 material being in particulate form and being dropped through the parallel lines of flux in a vertical direction under the action of gravity by a travelling wave vibratory feeder, the exit end of which is disposed vertically above the parallel lines of flux.
There may be two search coils connected in series opposition so that their response to a uniform external field is zero. The search coils may be movable one relative to the other for setting-up purposes whereby the detector may be zeroed by relative movement of the two search coils, the search coils being then fixed relative one to the other during normal operation of the detector. There may be provided further means to remove the ferromagnetic particles from the non-ferromagnetic material after detection thereof.
The removing means may comprise an interrupter to interrupt the flow of material through a passageway to prevent that portion of the material containing the ferromagnetic particles from passing to a receptacle. The interrupter may comprise a plate~
By way of exa~ple only an e~bodiment of the invention will now be described with reference to the accompanying diagrammatic drawings of which:
Figure 1 is a schematic cross-section of a magnet and search coil assembly;
Figure 2 is a schematic cross-section of a detector and separator unit; and Figure 3 is a schematic view of the deflector plate of Figure 2.
E
~122669 A pair of magnetic search coils 1,2 which form a conventional magnetometer is located within the centre of a DC electromagnetic solenoid 3. The solenoid provides a zone, in which the coils 1,2 are located of substantially constant field with the flux lines being disposed parallel to one another and in a vertical direction.
Surrounding the solenoid 3 is an iron shield ~ and an electrostatic screen 5 defines a bore within the iron shield through which passes a tube 6 of dielectric material such as glass. Titanium swarf which may include ferromagnetic lumps passes vertically down through the tube 6 in a lamellar manner in the direction of the arrow 7 under the action of gravity. Any ferromagnetic material in the stream of scrap is magnetised by the solenoid 3 and movement of the magnetised particles through the search coil produces a voltage output from the coil and this can be detected by suitable voltage means not shown.
It is important, when using a titanium swarf that the passage of the particles through the solenoid should be parallel to the lines of force, if the particles were to move across the width of the tube 6 they would cross the parallel lines of flux, and in crossing the flux lines would generate eddy currents which would give rise to a magnetic field which would be picked up by the search coils. This would therefore give a false indication of the presence of a ferromagnetic material, consequently operating in error the rejection mechanism described below. It will be understood, therefore, that when using a conducting matrix it is important to use a method of feeding which provides for the passage of particles through the solenoid in a parallel manner. Particular examples of this method are described below.
~Z2669 The detector means may supply an output signal to any form of suitable indicator such as a meter or light signal. The meter may be connected to means to reject the particle from the stream.
Such a means could be an air jet connected to the detector through a suitable delay circuitry. The electrical circuitry is of a conventional type and is not part of the present invention. The use of two search coils enables the system to be relatively insensitive to externally generated electromagnetic fields. Although a single coil could be used and electronic amplification of the necessary sensitivity is readily available the presence of fluctuating electro-magnetic fields makes it difficult to use this sensitivity in practice.
Referring to Figures 2 and 3 these show a separator unit incorporating the detector of Figure 1. Titanium swarf is passed in the direction of arrow 10 into a feeder trough 11. The feeder trough 11 is a vibratory feeder which works by establishing a travelling wave in material located on the surface of the feeder. Particles on the moving surface of the feeder are moved forwards by the action of the travelling wave and eventually arrive at the exit end of the feeder which is located above a guide tube 12. The particles are simply moved over the end of the exit end without being given a forward component of movement thereby dropping straight down through the guide tube 12. If a conveyor belt, for example, were to be used to move material into the guide tube 12 it would give the particles a forward or translational movement which would not be damped by the guide tube and thus the particles would fall down through the guide tube and would ricochet or bounce off the walls of the guide tube and would set up eddy currents within the search coils.
-' ' : ' . . : .
~lZ266~
An alternative method of passing the particles in a lame]lar manner through the guide tube is to entrain them in a moving air stream such that the particles are accelerated initially to space out the particles and damp translational movement and have them moving in a parallel manner vertically downwards in the region of the search coils 1 and 2.
The exit end of the feeder 11 preferably is smaller than the guide tube 12 so that the particles can fall freely through the guide tube.
The exit end of the feeder is conventionally referred to as the gate and the gate width is preferably less than the cross-sectional size of the tube 12.
This feeder passes the swarf into the guide tube 12 which is arranged vertically to permit the swarf to pass down through the detector unit indicated generally by 13. An inclined plate 14 can act to deflect swarf when in the position illustrated through chute 15 into receptacle 16.
If the inclined plate 14 is not in position the swarf will fall through chute 17 into receptacle 18. The inclined plate is driven as is shown more clearly in Figure 3.
In Figure 3 the plate 14 is movable by means of air-operated cylinders 19,20 to obscure hole 21 which is the extension of tube 12.
Thus as long as plate 14 is in the retracted position as shown in Figure 3 swarf will fall through the tube 12 and tube 17 into receptacle 18.
Upon detection of a ferromagnetic particle cylinders 19 and 20 push plate 14 over aperture 21, deflecting the particles through tube 15 into receptacle 16. Obviously the deflected particles will include non-ferromagnetic material as well as the ferromagnetic material because the response time of the equipment would not be sufficiently accurate only to deflect the ferromagnetic material. This swarf ~1226E;9 can, however, be recycled by periodically removing the contents of receptacle 16 and passing them through the machine again. In order that it can be obvious that the machine is working large plastic balls containing small quantities of ferromagnetic material can be inserted through funnel 21 as shown at 22. These parts will operate the machine and be deflected thereby proving that the machine is functioning and acting as a continuous monitor and indicator. This visual signal can be used to reassure the operators that the machine is working satisfactorily.
With the two search coils mounted inside the magnetising solenoid and being connected in series opposition their response to a change in external field is zero. As the magnetic particles fall consecutively through each coil a voltage pulse in the series circuit is produced as each particle leaves the upper search coil and enters the lower.
If the search coils each enclose the same number of area turns (area of cross-section times the number of turns) and are mounted in the magnetic centre of the magnet the system does not respond the fluctuations in the magnetising current. Fine corrections may be made by slightly moving the two coils within the magnet to the place where the minimum electrical noise is picked up. The iron shield is used because without it the system tends to respond to non-uniform external fields as the fields in each of the search coils may be different.
Electrostatic screening is provided as shown and of course the electrical leads from the search coils to the amplification means should also be screened.
Because the magnetic flux enclosed by the pair of search coils depends on the position of the coils within the solenoid relative motion between the two will also cause electrical noise. It is -- -- --~ , ~122~6~
important therefore that the search coils be rigidly attached to each other and to the solenoid. In addition the central tube down which the particles fall should be separated from the search coils in order that mechanical vibration or electrostatic pick up be reduced.
A version of the invention having a solenoid which produced a field of 0.1 Tesla in a bore of 72mm diameter was tested with search coils each having 67 000 turns at a diameter of 30mm.
Titanium swarf contained in particles of tungsten carbide tool tip of mass 2 x 10~3g was dropped through the central tube. A pulse of 0.2mV and 20ms duration was generated. The background from the uncontaminated titanium swarf was small, being less than 0.02mV.
It will be appreciated that typical tool tip material comprises only 5 to 15% by mass of ferromagnetic material. Consequently, the detector is capable of determining the presence of 0.1mg of material with ferromagnetic susceptibility.
It will be appreciated that the invention is not limited to the detection of ferromagnetic material in titanium swarf. The apparatus may simply be used if necessary after calibration to detect any ferromagnetic material in a non-magnetic matrix, such as food, ie peas, beans, currants etc, or other non-magnetic material such as brass, copper, or wood chips.
;~
Claims (23)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of detecting particles of tool tips containing a ferromagnetic material in a matrix of metallic non-ferromagnetic material which comprises the steps of passing the matrix through a detector unit, the detector unit compris-ing magnetic sensor means located within an area of applied magnetic field, the applied magnetic field having a substantially constant zone in which the magnetic sensor means is located, the applied magnetic field being generated by an electromagnet which is so disposed that the uniform magnetic field has parallel lines of flux in a vertical direction, the matrix material being passed vertically downwardly through the field parallel to the lines of flux in a lamellar manner at least in part under the action of gravity.
2. A method as claimed in Claim 1 in which the particulate material is fed to the detector unit by a travelling wave vibratory feeder the exit end of which is disposed vertically above the parallel lines of force.
3. A method as claimed in Claim 2 in which the particulate material falls through a tube and the exit end of the vibratory feeder has a smaller gate size than the cross-sectional size of the tube through which the material falls.
4. A method as claimed in Claim 1 in which the particulate material is passed through the magnetic field in a forced air flow which accelerates the particles before passing the particles through the field.
5. A method as claimed in Claim 1 in which two search coils are connected in series opposition so that their response to perturbations in the uniform external field is zero.
6. A method as claimed in Claim 1 in which the sensor means is of tubular or ring like formation.
7. A method as claimed in Claim 1 in which there is provided an iron shield around the magnetic sensor and field generating member.
8. A method as claimed in Claim 1 in which there is provided an electrostatic screen within the sensor means.
9. A detector for detecting ferromagnetic material in a matrix of non-ferromagnetic metallic material which includes a search coil located within an electromagnetic field of substantially con-stant strength and means to detect in use a voltage generated through the search coil on the passage of a ferromagnetic material through the search coil, the field being generated by an electro-magnet and having a plurality of parallel lines of flux disposed in a vertical direction, the matrix material being in particulate form and being dropped through the parallel lines of flux in a vertical direction under the action of gravity by a travelling wave vibratory feeder, the exit end of which is disposed vertically above the parallel lines of flux.
10. A detector as claimed in Claim 9 in which there are two search coils connected in series opposition so that their response to a uniform external field is zero.
11. A detector as claimed in Claim 10 in which the search coils are movable one relative to the other for setting up purposes whereby the detector may be zeroed by relative movement of the two search coils, the search coils being then fixed relative one to the other during normal operation of the detector,
12. A detector as claimed in Claim 11 in which there is provided further means to remove the ferromagnetic material from the partic-ulate non-ferromagnetic matrix after detection thereof.
13. A detector as claimed in claim 12 in which the means comprises an interrupter to interrupt the flow of material through a passageway to prevent that portion of the material containing the ferromagnetic material from passing to a receptacle.
14. A detector as claimed in claim 13 in which the interrupter comprises a plate or air jet.
15. A detector as claimed in claim 9 in which the search coil is of tubular or ring-like formation.
16. A detector as claimed in claim 10 having an iron shield around the search coil and the field generating electromagnet.
17. A detector as claimed in claim 10 having an electrostatic screen within the search coil.
18. A detector as claimed in claim 10 in which the vibratory feeder has an exit end with a smaller gate size than the cross-sectional size of the search coil.
19. A method as in claim 1 wherein said non-ferromagnetic material is titanium swarf.
20. A method as in claim 1 wherein said ferromagnetic particles are separated from said non-ferromagnetic particles after detection by movement of a deflector plate to a position beneath the sensor means.
21. A method as claimed in claim 1, 2 or 3 in which at specified times a known ferromagnetic material or a container containing a known ferromagnetic material is passed through the detector unit to confirm satisfactory operation of the detector unit.
22. A method as claimed in claim 4, 5 or 6 in which at specified times a known ferromagnetic material or a container containing a known ferromagnetic material is passed through the detector unit to confirm satisfactory operation of the detector unit.
23. A method as claimed in claim 7 or 8 in which at specified times a known ferromagnetic material or a container containing a known ferromagnetic material is passed through the detector unit to confirm satisfactory operation of the detector unit.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB4015/77 | 1977-02-01 | ||
| GB401577A GB1570640A (en) | 1977-02-01 | 1977-02-01 | Magnetic detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1122669A true CA1122669A (en) | 1982-04-27 |
Family
ID=9769153
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,268A Expired CA1122669A (en) | 1977-02-01 | 1978-02-01 | Magnetic detector |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS53121648A (en) |
| CA (1) | CA1122669A (en) |
| DE (1) | DE2804090A1 (en) |
| FR (1) | FR2379077A1 (en) |
| GB (1) | GB1570640A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017205958A1 (en) * | 2015-06-02 | 2017-12-07 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2494447A1 (en) * | 1980-11-14 | 1982-05-21 | Radiotechnique | Moving metal component detector for automatic machine - uses presence of metallic object passing through coil to stop oscillatory circuit and provide output from monostable |
| DE3840848A1 (en) * | 1988-12-03 | 1990-06-07 | Draegerwerk Ag | MATERIAL WITH PRESETABLE MAGNETIC SUSCEPTIBILITY |
| GB8920957D0 (en) * | 1989-09-15 | 1989-11-01 | Hitech Metal Detectors Ltd | Metal detecting apparatus and apparatus for testing metal detecting apparatus |
| WO1992001956A1 (en) * | 1990-07-20 | 1992-02-06 | John Lysaght (Australia) Limited | Strip position sensor |
| DE19830584C2 (en) * | 1997-10-11 | 2001-11-22 | Mesutronic Geraetebau Gmbh | Sensor device |
| DE19954716B4 (en) * | 1999-11-13 | 2006-08-31 | Mesutronic Gerätebau GmbH | Function test for a metal detector |
| CN101571598B (en) * | 2009-05-26 | 2011-07-27 | 包剑刚 | Detector for small iron parts |
| CN104549726B (en) * | 2015-01-04 | 2017-01-25 | 湖北省地质勘查装备中心 | Medium-magnetism electromagnetic sorter |
| CN112824871B (en) * | 2019-11-20 | 2022-11-15 | 中国南方电网有限责任公司超高压输电公司贵阳局 | Grounding grid defect diagnosis method based on transient electromagnetic apparent resistivity imaging technology |
| CN116380163B (en) * | 2023-03-29 | 2024-01-19 | 青岛峻海物联科技有限公司 | Sensing device for intelligent environment data acquisition of Internet of things |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2045769A (en) * | 1928-05-31 | 1936-06-30 | Rca Corp | Electrical control circuit |
| US2315045A (en) * | 1939-10-09 | 1943-03-30 | Illinois Testing Laboratories | Metal detection device |
| US2444751A (en) * | 1946-02-12 | 1948-07-06 | Western Electric Co | Method and apparatus for sorting magnetic materials according to their residual magnetism |
| FR928347A (en) * | 1946-05-20 | 1947-11-25 | Improvements to devices for detecting ferrous or magnetic bodies or irregularities which exist in ferrous or magnetic objects | |
| JPS51120792A (en) * | 1975-04-16 | 1976-10-22 | Densoku Kogyo Kk | Device for detecting metals mixed in fluids |
-
1977
- 1977-02-01 GB GB401577A patent/GB1570640A/en not_active Expired
-
1978
- 1978-01-31 FR FR7802708A patent/FR2379077A1/en active Granted
- 1978-01-31 DE DE19782804090 patent/DE2804090A1/en not_active Ceased
- 1978-02-01 JP JP1037778A patent/JPS53121648A/en active Pending
- 1978-02-01 CA CA296,268A patent/CA1122669A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017205958A1 (en) * | 2015-06-02 | 2017-12-07 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
| US10274630B2 (en) | 2015-06-02 | 2019-04-30 | Syncrude Canada Ltd. In Trust For The Owners Of The Syncrude Project As Such Owners Exist Now And In The Future | Tramp metal detection |
Also Published As
| Publication number | Publication date |
|---|---|
| DE2804090A1 (en) | 1978-08-24 |
| FR2379077B1 (en) | 1984-05-25 |
| FR2379077A1 (en) | 1978-08-25 |
| JPS53121648A (en) | 1978-10-24 |
| GB1570640A (en) | 1980-07-02 |
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