US1861687A

US1861687A - Magnetic control system

Info

Publication number: US1861687A
Application number: US505862A
Authority: US
Inventors: William B Cooley
Original assignee: Hevi Duty Electric Co
Current assignee: Hevi Duty Electric Co
Priority date: 1929-09-03
Filing date: 1930-12-31
Publication date: 1932-06-07
Anticipated expiration: 1949-06-07

Description

June 7, 1932. w, COOLEY 1,861,687

MAGNETIC CONTROL SYSTEM Original Filed Sept. 3, 1929 VOLT/162' INVENTOR.

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BY 6 041% A TTORNE;

cent material in a furnace for determining- Patented June 7, 1932 l y l UNITED STATES PATENT OFFICE WILLIAM B. COOLEY, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO HEVI DUTY ELECTRIC COMPANY, OF MILWAUKEE, \VISCONSIN, A CORIORATION OF WISCONSIN MAGNETIC CONTROL SYSTEM Original application filed September 3, 1929, Serial No. 390,162. Divided and this application filed December 31, 1930.

My invention relates broadly to heat treatment furnaces and more particularly to a system for determining the condition of the material under heat treatment. It is a well established fact that the magnetic condition of steel is afiected by the application of heat 1 and that a certain relationship exists between r 1929, and entitled Magnetic control system.

One of the objects of my invention is to provide a system for electrically determining the time at which magnetizable material treated in a heat treatment chamber may reach a condition or reference point, from which subsequent operations can be determined, and where the electrically determin ing means is operatively independent of the source of heat which may be supplied to the heat treatment chamber.

Another object of my invention is to provide a magnetic system positioned adjacent material which is subjected to heat treatment in a heat treatment furnace, for determining the condition of the material under heat treatment operatively independent of the heat source which is applied to the furnace.

Still another object of my invention is to provide a magnetic system. disposed adjathe condition of material which is subjected to heat treatment, the magnetic system being entirely independent of the heating means which is supplied to the furnace.

A further object of my invention is to provide a magnetic system inductively related to material in a furnace for determining the condition of material which is being subject ed to heat treatment, and in combination therewith, but separate from the magnetic system, another system for automatically controlling the temperature of the furnace without alfecting the magnetic system.

A still further object of my invention is Serial No. 505,862.

to provide a magnetic. system for controlling the time period over which material within the furnace is subjected to heat treatment in accordance with the condition of the material within the furnace and independently of means by which the material in the furnace may be heated.

Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accompanying drawing which diagra1nmatically shows the arrangement of the parts of the furnace and circuit for indicating the magnetic permeability of the charge under heat treatment therein.

My invention is directed to a magnetic indicator and control system for heat treatment furnaces, wherein the point at which the steel or other magnetizable metal under heat treatment changes its magnetic properties upon heating, may be detected so that heating may be discontinued, or the temperature modified, or the steel withdrawn, or permitted to remain in the furnace for definite subsequent periods at the discretion of the operator. My

' invention makes use of the principle that steel or other magnetizable metal changes its magnetic properties when heated to certain temperature, depending upon the analysis of the steel. This change of magnetic properties, occurring at a positive transformation or critical point in the steel, establishes when known, a refernce point in the heat treatment. My invention provides for magnetically determinin g the point at which the steel or other metal under heat treatment changes its magnetic properties, or has reached a definite transformation point, so that the proper heat treatment can be determined, the magnetic determining means operating independently of the heating source.

In the system of my invention, a heat treatment furnace is provided with any form of heating means such as gas, or other fuel, or resistors which are electrically energized. I provide a magnetic core of high permeability which surrounds the refractory shell of the heat treatment furnace terminating in pole pieces aligned on opposite sides'of the charge under heat treatment.

The pole pieces carry chamber 28.

electromagnetic windings which are connected in a power supply circuit through a coupling device. An indicating apparatus is connected in circuit with the coupling device. The magnetic path provided around the magnetic core is interrupted by the air gap across the furnace. \Vhen the charge is introduced in this air .gap within the furnace, the magnetic conditions of the magnetic path through the core is changed. Pre'determine'd magnetizing force may be supplied to the magnetic circuit and calibrations placed upon the indicating apparatus showing the normal magnetic readings when the charge is introduced into the furnace. As the charge is subjected to heat treatment, a change in the magnetic properties occur which changes are readily observed by the indicating apparatus. As the charge approachesthe critical transformation point, the changes are detected by the indicating apparatus and the character of subsequent heat treatment to be given to the material within the chamber may b'e'determined.

Referring to the drawing in detail, the furnace chamber is designated at 28 having a charge 29 shown schematically therein. An electric heating system is shown including heating elements 4 arranged adjacent *the charge in the furnace and energized from an. independent power supply source which connects to terminals 5. The heating circuit is maintained entirely separate and distinct from the magnetic measuring circuits hereina'fter described. The magnetic circuit is indicated as formed bycore 30 of high magnetic permeability terminating in

pole pieces

31 and 32 on opposite sides of the furnace These pole pieces are directly aligned with the charge 29 within furnace chamber '28. Magnetic win-

dings

31 and 34 are positioned upon. the pole pieces 31 an'd '32 for establishing a permanent magnetic field through the furnace chamber with thecha rge 29 forming part of the :path thereof. The high magnetic permeability of the core 30 increases the strength of the magnetic flux in thepaththrough the furnace chamber and renders slight variations due to changes in the magnetic conditions of the charge 29 observable with great accuracy. A compensa tor connects between'the windings 35 and -34 as shown at 12. The compensator 12 includes primary winding 15 and secondary winding 14. The energizing circuit labeled line voltage connects to one end of primary winding 15 and t-OOHQtLIXIlOf thQ winding 34 on pole piece '32. The opposite end of winding 34 connects to the opposite end of primary Winding 15,'thus-completing the primary circuit. The secondary winding includes winding 14 o'fthe compensator 12'connecte'dinseries through winding 35 on pole piece 3 l and inseries with the indicator -16 returning tO the opposite end of the secondary winding 14,

thus completing the secondary circuit. The compensator 12 has an adjustable core 17 for balancing purposes.

By the proper adjustment of the compensator which includes movable core member 17, galvanometer 16 may be deflected to a predetermined or zero condition indicating a position of balance of the magnetic flux through the furnace chamber without the charge 29 in position therein. Upon introduction of the charge 29 the galvanometer or indicator 16 is deflected by virtue of the increased flux which passes through the furnace chamber in the path partially closed by the steel or magnetizable charge 29. Under conditions of continued heat treatment, the charge 29 changes its magnetic properties and when that transformation point is reached, the heating cycle "can be concluded, or the operator, by noting the change of magnetic properties of the charge 29 by reading the galvanometer 'or indicator 16, can cut off the sup- :ply of heating energy from the circuit 5 by any suitable means such as the customary switch, 'orzhe may elect to soak the charge for any subsequenttime.

While I have described my invention in-one of its preferred embodiments, I desire that it is understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as :new and desire to secure by Letters Patent-of the United States is as follows:

1 A furnace comprising a chamber adapted to receive a charge, a heating element in said chamber, a source of electric "current, a primary andsecondaiy'coil having a common core of material of high permeability, an air gap in the magnetic circuit so disposed that the lines of force pass through the charge within said chamber, and means responsive to inductive effects of the primer c'oi'l and con'neoted with said secondary coll :foriindicating the magnetic properties ofsaid change during the heating process.

2. A magnetic control system for heat treatment furnaces comprising in combination with "a furnace chamber adapted to :re-

oeive a charge for "heat :treatment, heating means within said chamber, a magnetic core memberextending exteriorly of said chamber and terminating in pole pieces aligned with the charge within said chamber, magnetic "windings disposed'on saidipole piecesyacompensatorhavinga pair-of windings connect- :ed in circuitwith themagnetic windings on 'saidpole pieces, a source of potentialin circuit withone of the windings of said pair of windings, 'and an indicator connected in circuit 'With the other of said windings of :saidip'air ofxwindings ifor indicating theimagnetic permeability "of the charge within the furnace during the :processof-heat treatment. 139

3. A furnace comprising in combination a heating chamber adapted to receive a charge of magnetic material disposed within said chamber, heating means for said charge within the chamber, a magnetic core extending around said chamber and terminating in a pair of pole pieces exterior of said chamber and aligned with said charge whereby said charge forms a portion of a path for magnetic flux through said core, electromagnetic windings on said pole pieces, a compensator having a primary and secondary winding, a source of potential in circuit with said primary winding and one of said electromagnetic windings, a meter connected in circuit with said secondary winding and the other of said electromagnetic windings for indicating changes in the magnetic condition of the charge within the furnace during the heat treatment process.

4:. A furnace including a heat treatment chamber adapted to receive a charge of magnetizable material, means for heating said charge, a magnetic core member extending around said chamber and terminating in oppositely disposed pole pieces directed toward each other and aligned with said charge whereby said charge forms a part of a path for magnetic lines of force through said core, a source of potential, a compensator having a pair of inductively related windings, an indicating meter, electromagnetic windings on said pole pieces and series connected circuits each individual to one of the windings on said compensator and one of the electromagnetic windings on said pole pieces, one of said circuits having a connection to said source, and the other of said circuits having a connection to said meter for indicating on said meter the change of magnetic properties of said charge during the heat treatment process.

5. In an electric furnace, a heat treatment chamber adapted to receive a charge of magnetizable material, means for heating said charge, a magnetic core extending around said chamber and terminating in pole pieces directed toward said charge in alignment one with the-other, a magnetic compensator including a pair of inductively related electromagnetic windings on said pole pieces, a source of potential, a circuit connection between one of the windings of said compensator and one of the electromagnetic windings on said pole pieces with said source of potential and another circuit connection between the other winding of said compensator and the electromagnetic winding on the other of said pole pieces with a meter for indicating on said meter changes in the magnetic properties of said charge.

In testimony whereof I afiix my signature.

WILLIAM B. GOOLEY.