Electric heating – Metal heating – Of cylinders
Patent
1987-02-26
1988-10-25
Leung, Philip H.
Electric heating
Metal heating
Of cylinders
219 1055M, 219 1055F, 219 1061R, 219 1075, H05B 678
Patent
active
047805854
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a method and a device for the thermal treatment by Joule effect of a conductor element at least partially constituted by a conducting material.
The method and device according to the invention are in particular adequate for heating a conductor element of the above mentioned type, advantageously in a filiform shape and specially in the shape of fibers, which carries a continuous or discontinuous coating of a material, specially based on a polymeric product susceptible to become heated by thermal conduction and for that reason to soften or harden, depending on whether said material is thermoplastic or thermosetting, to form a homogeneous coating of the conductor element.
It is known that any electric conductor having an ohmic resistance is the seat of a heating by Joule effect when it is traversed by an electric current.
The use of a direct electric current for heating a conductor and specially an advancing conductor is well known and gives satisfactory results provided that the contact resistances at the inlet point of energy be very weak in relation to the resistance of the conductor.
When the conductor carries a thermofusible or thermosetting coating of insulating nature such as a coating obtained by deposit of a powdered polymeric material, the presence of said coating interferes with the conditions of good contact. For this reason it is no longer possible to carry out a satisfactory fusion or setting of such a coating by passing a direct electric current into the conductor carrying said coating for obtaining a homogeneous coating of said conductor by the thermofusible or thermosetting coating material.
There has been described already (French No. A-1569046) continuously heating a dielectric material covering a filiform element conductor of electricity by means of microwaves by having recourse to a device including a coaxial conductor comprising a conducting covering closed at both ends by conducting elements and two tubular conducting cores aligned and separated from each other by a predetermined space, which are fixedly situated in the interior of the covering and coaxially to the latter. The heating is carried out by making the filiform element covered with dielectric material circulate in the interior of said two tubular cores and by subjecting said dielectric material in the space separating the two conducting cores to the action of an electric field created by microwaves produced in the coaxial conductor by transfer to the latter, by means of an electronic adapter, of the microwave electromagnetic energy delivered by a generator.
The above mentioned heating by microwaves, which is a heating of the type by dielectric losses, cannot be practiced other than with filiform conducting elements due to the necessity of making these elements pass to the interior of the coaxial conductor. Besides, said heating can only be carried out for coating materials of the filiform conductor element having dielectric losses at the frequencies used.
It has likewise been proposed (German No. A-1916870) to heat by microwave a metal conductor coated or not with a dielectric material by making the conductor pass into the interior of a conducting external cover advantageously provided with two short circuits capable to short circuit the metal conductor and the conducting external cover so as to form a coaxial line of leakages alongg which propagates the microwave electromagnetic energy transferred to the line from a generator by means of a coupling system of the wave guide type. The coaxial line leaks since, the microwave energy dissipates by Joule effect in the conductor and equally by dielectric leakages in the coating material of the conductor, in the coating material of the conducting external cover, and eventually in the area where the coaxial line is situated.
Such a mode of heating of metal conductor has certain inconveniences. In the first place, the mode of transmission to be selected for transporting the energy depends on the dimensions of the system, which changes the polarization of the fie
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patent: 3461261 (1969-08-01), Lewis et al.
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patent: 3571551 (1971-03-01), Ogasawara
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Gensous Francis
Lapoulle Bertrand
Rochas Jean-Francois
Tremillon Jean-Michel
Institut Textile de France
Leung Philip H.
Societe Nationale Elf Aquitaine
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