Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Reexamination Certificate
2001-10-30
2003-03-25
Strecker, Gerard R. (Department: 2862)
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
C324S164000, C324S207130, C324S226000, C324S229000, C324S235000, C073S861080, C073S861750, C073S514390
Reexamination Certificate
active
06538433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and device for measuring at least one parameter of a metal bed. By the term “metal bed” is meant metal in solid as well as liquid form. The term comprises arbitrary shapes of the bed and, thus, it is not limited to comprise an elongated web.
TECHNICAL BACKGROUND
In the industry, essentially the metallurgical industry, there is a great need for devices for measuring parameters, such as speed, of a metal bed in motion, for example, when controlling the metal flow in continuous casting or the stirring speed in a chill mould.
A device for measuring the speed of a molten metal is known from U.S. Pat. No. 4,144,756. According to this publication, the device comprises one coil which generates a magnetic field and two coils which have a receiving function. When the molten metal flows past the magnetic field producing coil, the charges in the molten metal sense a lorentz force, which gives rise to an eddy current that generates a second, or induced, magnetic field. The other coils receive the induced magnetic field and give rise to a signal via a circuitry, the signal being proportional to the speed of the molten metal. A drawback of the known device is, however, its fairly complicated design which has many components and that it is not reliable enough as regards ambient, disturbing fields, if any, which makes the device difficult to use. Another drawback is that the direction of motion of the metal flow cannot be determined by the device without the aid of other devices.
JP 57-199917 is included in Patent Abstracts of Japan and discloses an electromagnetic fluxmeter for molten metal. The fluxmeter comprises an annular, wound coil which is arranged circumferentially on a tube, in which metal flows. A magnetic field is generated by the annular, circumferential coil, whereby lines of flux parallel to the metal bed are formed. The magnetic field gives rise to eddy currents in the molten metal. A force which is related to the eddy currents affects the coil in the downstream direction of the metal flow. The circumferential coil on the tube is supplied with four load sensors which are relatively offset at an angle of 90°. The load sensors are used to measure the force which affects the circumferential coil, the force being proportional to the flow rate. A drawback of this prior-art construction is that it is very limited as regards possible fields of application, it is bulky and lacks the desired flexibility.
SUMMARY OF THE INVENTION
An object of the invention is to eliminate the problems of prior-art techniques by providing a method for measuring at least one parameter, such as the speed or the direction of motion, of a metal bed, the method being simple and reliable.
Another object of the invention is to provide a device for measuring at least one parameter of the metal bed, the device being simple, small and easy to handle.
Yet another object of the invention is to provide a device which is durable and which is easy to adapt to various applications and environmental conditions thereof.
The above-mentioned objects are achieved according to the invention by a method and a device which have the features defined in the accompanying claims.
According to the present invention, the problem of measuring a parameter of a metal bed is tackled in a new way by using a technique which, unlike the known electromagnetic detection, uses “mechanical” detection instead.
The invention is based on the knowledge that great flexibility and liberty of placing can be achieved by measuring from only one side of the metal bed. Nor is one bound to special dimensions of the metal bed but, on the contrary, the invention may advantageously be used for measuring on many different types of metal beds.
According to a first aspect of the present invention, a method is thus provided for contactless measuring of at least one parameter of a metal bed, the method comprising the steps of:
generating a magnetic field so that eddy currents are generated in the metal bed as the metal bed moves relative to the magnetic field, which is generated from only one side of the metal bed;
making the metal bed and the magnetic field move relative to one another;
adapting a means in connection with the metal bed so that it is subjected to the action of the force which is related to the eddy currents;
detecting the action of the force, which is induced by the eddy currents, on said means; and
determining the parameter of the metal bed on the basis of the detected force which is a function of the parameter.
According to another aspect of the present invention, a device is provided for contactless measuring of at least one parameter of a metal bed, the device comprising
first means for generating a magnetic field so that eddy currents are generated in the metal bed as the metal bed and said first means move relative to each other, said first means being adapted to generate the magnetic field from only one side of the metal bed;
second means which interact with the eddy currents and are arranged so that they are affected by a force which is related to the eddy currents; and
third means which are adapted to detect the action of the force on said second means, the detected force being a function of the desired parameter of the metal bed.
The device thus has a non-circumferential configuration and is designed to be placed on an optional side of the metal bed. Naturally, this gives a great possibility of selecting a measuring point and also of varying the distance to the metal bed.
The desired parameter may be any parameter that can affect the generated eddy currents and, thus, the force. Some examples of parameters are the speed of the metal bed as regards size or direction, the distance to the surface of the metal bed, the thickness or conductivity of the metal bed, or a combination thereof. Thanks to the device being placed on only one side of the metal bed, and preferably with such a suspension that its general extension is transversely of, preferably substantially perpendicular to, the metal bed, motions in all directions in the plane of the metal bed can be detected.
The device for measuring a parameter of a metal bed according to the present invention comprises first means for generating a magnetic field so that parameter-dependent eddy currents are generated in the metal bed as the metal bed moves relative to said first means. Said first means are conveniently adapted in such a manner that the generated magnetic field is directed towards, preferably substantially perpendicular to, the metal bed. In other words, the central lines of flux are preferably substantially perpendicular to the metal bed. Said first means may comprise one or more permanent magnets, one or more electromagnets with an iron core and/or a powder core, or a combination of permanent magnet(s) and electromagnet(s). A permanent magnet is preferably arranged so that the axis which is defined by the north pole and the south pole is substantially perpendicular to the metal bed. In the case of an electromagnet, the axis of the coil is preferably directed perpendicular to the metal bed.
The device further comprises second means which interact with the eddy currents and are adapted in such a manner that they are affected by a force which is related to the eddy currents. Preferably, the main direction of the generated magnetic field forms a substantially right angle to the direction of said force which affects said second means. Said second means comprise, for example, a magnet which is arranged on a pendulum or is included in a pendulum, magnets which are arranged on a wheel or are included in a wheel, or a fixedly attached element, in which stress arises under the action of the force.
The device also comprises third means which are adapted to detect the action of the force on said second means, the detected force being a function of the desired parameter of the metal bed. Said third means comprise, for example, Hall sensors, double-pulse lasers, strain gauges, pressure gauges, hydraulic or pneumatic means, magneto
Cervantes Michel
Enström Christer
Kelvesjö Håkan
Ohlsson Willy
MPC Metal Process Control AB
Strecker Gerard R.
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