US1868954A - Furnace - Google Patents

Description

Patented July ze, I1932 UNITED sTATEs PATENT OFFICE VICTOR BORREL AND MUIS ANDR LAFONT, F GRENOBLE, FRANCE, ASSIGNORS T0 'UGINE-INFRLPF GRmORLE, IRANC1-A CORPORATION 0F FRANCE Application med Uctober 18, 1999, Serial lo. 00.883, and/in France lay 8, 1929.

This invention relates to a continuously working furnace for the heat treatment of metals and other substances. There are a1- ready known various t pes of continuously l working'furnaces for t e heat treatment of metals and other substances, whichfurnaces 1 are characterized by the parts or objects to be treated (ferromagnetic parts or parts placed within a ferro-magnetic sheath or envelope) being stopped by the action of an electromagnetic feld until they reach the temperature at which their magnetism disappears. v

It has been proposed to arrange furnaces of this kind in such a manner as'to enable the objects 'to be treated to be 'left therein for a certain len h of time after their demagnetization, 1n order to bring them to a temperature hi her than that at which their magnetism `sappears, this temperature, for

5 instance, ensuring their hardening. l

In order to obtain this result, in certain kinds of furnaces, the ob'ects were allowed to slide into an inclined tu ular heating mule under the action of gravity, the descent in u question being assisted if reciired by means of shocks imparted to the tu .Y

The object of the present invention is to provide a type of continuously workin furnace enabling the duration of stay of t e objects .in the furnace, after their. passage through the point of demagnetization, to bel regulated in as exact a manner as posslble so that the discharge of said objects from the furnace may be effected at any desired time u after they have reached the point of demagnetization, and with that end in view, the advance of the objects in the furnace is to be effected not by gravity but by means of magnetic attraction 'constantly exerted on the o still magnetic objects by one or more suitably arranged electromagnets. Y

The magnetic objects introduced into the furnace thus constitute in eiect a flexible magnetic chain which constantly progresses 5 in a uniform manner under the attraction of the electromagnet or electromagnets, and continuously pushes the objects after they have passed the point at which they become demagnetized to the point of their discharge 5 from the furnace.

c By means of this arrangement, it is possible to obtain for instance an absolutely uniform temperature and the hardening of steels vor other materials, and to use the furnace for other operations such as normalizing or hot 55 working. i

In order to produce this continuous attraction of the objects introduced into the furnace by means of one or more electromagnets, it is advisable to arrange the latter in such 00 a manner that their pole pieces are in close proximity to the refractory muilie containing the objects to be treated, the exciting winding of the said electromalnet or electromagnets being arranged at wi l either in the interior 05 of or outside, the heat-nonconducting walls of the furnace. It will be sufficient therefore to use an electromagnet of a relatively small power for obtaining the desired result.

The present invention comprises also several characteristic detailed features which will be more fully described hereinafter.

The accompanying drawing shows diagrammatically, by way of example, two constructions 'according to the invention in 75 longitudinal section.

I'n Figure 1, the furnace is constituted by a horizontal refractory maille 1 of a material which is nonrnagnetic at the temperatures of v its utilization, and surrounded with a suitso Vable heat nonconducting material 2 enclosed in a casing 3. l

The muflle 1 is heated in any known manner, for instance by means of resistances 4 through which runs an electric current.

The objects A to be treated are introduced one afteranother into the muiiie 1 and exposed to the action of an electromagnet 5 with direct or rectified current, the pole pieces of which, constituted by a refractory magnetic metal or alloy with a very high point of demagnetization (cobalt, ferro-cobalt etc.) are arranged in the interior of the heat nonconducting material 2 quite close to the mufle 1.

The exciting winding of the said electromagnet 5 is preferably, but not necessarily, locatedas shown in the interior of the lagged walls of the furnace.

Owing to this arrangement, even with an 10 electromagnet of a relativelysmall power,

' each of the objects A to be treated introduced l into the muile 1, will cease to beattracted by the electromagnet 5 only when the temperature causes its magnetism to disappear entirely. y

The ferro-magnetic objects which have been introduced into the mufHe and have notv yet reached the temperature of transformation. will form therefore in effect a magnetic chain constantly attracted by the electromagnet 5 which tends to advance it in the furnace; owing to the continuous thrust which it exerts on the object undergoing treatment after their magnetism has disappeared, continuous discharge of the said objects is ensured.

The magnetic chain constituted by the objects introduced into the furnace and still magnetic, pushes incessantly the objects which have already lost their magnetism along the part a-b of the sole of the inutile to the point b where the said parts are discharged'froni the furnace, the said discharge taking place either on an inclined plane 6 or by moans of any suitable mechanical or hand operated device.

1Whenever a hot object A is discharged at the end of the mufile, a new object is introduced at the point c, and there is produced from .c to d a regularly increasing range of temperature. such .that the objects constantly arrive at al in a state of close proximity to their point of vmagnetic transformation.

With such an arrangement, a perfect precision is obtained in the heating of the objects A to be treated to the predetermined temperature, which precision will be the greater i as the magnetic field which acts on them is entirely localized in the neighbourhood of the objects to be treated, so that it cannot be disturbed by causes external to the furnace.

The output ofthe furnace in objects raised to the predetermined temperature, is in fact exclusively the function of the characteristics of the furnace in its part c-cl which constitutes a real motor unit, the factors being the intensity of heating from c to d, the length c-Z, the regulation of the intensity of the magnetic field of the electromagnet 5 and, finally, the temperature with which the objects A to be treated are introduced at c.

This advance of the objects under the action of the magnetic chain,'before as well as after their passage through the point d of dis- Y appearance of their magnetism. makes it posfra sible without the intervention in any way of the forces of gravity, to obtain a perfectly exact regulation of the length of stay of the j objects in the furnace after their passage through the point of transformation, and consequently to obtain absolute precision and uniformity of heating of the objects treated.

It desired, the movement of advance of the magnetic chain may be of course assisted by combining the force of magnetic attraction of the electromagnet 5 with a. suitable additional force applied to the chain by any known means, it being however understood thatin no case the intensity of this additional force should be suficient toproduce alone the ad.

vance of the objects undergoing treatment.

It must be pointed out that the furnace bef ing normally fed and its heating correctly adj usted, the temperature of the muiile at each of its points will tend to be 'in equilibrium with the temperature of the object which at the moment 1s at this point. lMore particularly, at the point d, the furnace will assume a constant working temperature slightly higher than that which corresponds to the demagnetization of the objects.

The furnace may comprise moreover a dif- :terential pyrometer, one of the hot points 7' 'of which will be placed at d and the other one 7 at t so as to enable the temperature at thelatter point to be regulatedto a degree suitable for the heating to the predetermined temperature of the objects being treated.

In the construction shown in Figure 2, are to be ound the same elements and the same parts as in Figurel, but'there is provided in addition, outside the mue l, a solenoid 8 traversed by a direct or alternating electric current and arranged in' such a manner that the electromagnet 5 is in a uniform field zone of the solenoid- Owing to this arrangement, the chain of the objects A always tends to penetrate into the interior of the solenoid which thus adds its action to the attraction of the electromagnet 5 so as to produce the desired advance of the objects.

vln the case of electrically heated furnaces, the heating winding 4 itself may be arranged and built so as to act as the said solenoid 8.

In both Figures 1 and 2, there is shown moreover an auxiliary electromagnet 9, the

pole pieces of which are also arranged in the interior of the frame of the furnace and in immediate proximity the mume. Under the action oi the magnetic field of the said electromagnet (with alternating current or rectified current), the objects A to be treated are exposed to continuous vibrations which avoid their catching or becoming hooked and regulate their progression or advance. This arrangement is not imperative of course,

and the same result may be obtained by any bands, bars or Wires, the principle ofl the' furnace remains exactly the same, except that the magnetic chain is then formed naturally. It at their admission and at their exit from the muliie, the products to be treated are Wound as usual on reels or any driving devices actuated mechanically by an auxiliary motor or motors supplying to these Winding devices a certain torque, it 'will be necessary that in order to render the system of furnace described applicableV to this arrangement, said torque should be always smaller than the magnetic advance torque exerted by the electromagnet-or the solenoid on the magnetic chain.

lVe claim: v

1. The methodof treating magnetic objects for purpose of demagnetization and heating which consists in causing said objects to pass in a contiguous series or chain through a magnetic field within the heating zone of a furnace, said objects being advanced by the attraction of said magnetic field, the

objects not yet demagnetized acting to push those in front of them, said magnetic field acting also to detain said objects until each is completely demagnetiaed and has reached the predetermined temperature. e 2. A continuously working furnace for th heat treatment of metals comprising a mule having a passage therethrough, electro-magnetic means creating within' said mule a magnetic field constantly exerting an attractive force on the objects undergoing treatmentto draw the same along said passage and to s advance a series of contiguous objects bythe pressure of each upon those in front of it, said passage being approximately horizontal for the greater part of its length.

3.. A continuously Working furnace for the heat treatment of metals comprising a mulile having a passage therethrough, electro-magnetic means creating within said muie a v magnetic field constantly exerting anattractive force on the objects undergoing treatto advance a series of contiguous objects by the pressure of each upon those infront of it, and a solenoid surrounding said passage.

4. A continuously working furnace for the i heat treatment of metals comprising a. mullie having a passage therethrough, electro-magnetic means creating within said muflle a magnetic field constantly exerting an attractive force on the objects undergoing treatment to draw the same along said passage and to advance a ,series of contiguous objects by the pressure of each upon those in front of it, and an auxiliary electro-magnet `disposed in advance of said first named magnet so as to subject the objectswhich have not yet become demagnetized to vibrations. In testimony whereof We have signed this specification.

VICTOR SORREL.

Louis ANDR LAFoNT.

ment to draw the same along said passage and

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