DE1237239B - Circulating drying cylinder with fixed induction heating device arranged inside - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Number:
File number:
Registration date:
Display day:

H05b

German KL: 9 p.m.-12

E 26465 VIII d / 21h

February 22, 1964

March 23, 1967

The invention relates to a rotating drying cylinder, for. B. for paper webs, with internally arranged, fixed induction heater.

Drying cylinders of this type are known from German Auslegeschrift 1151724, for example. at the embodiment described there is inside a circumferential cylinder jacket concentrically at least one stationarily arranged with AC excited induction coil is present, the turns of which are near the inner surface of the Cylinder jacket run. The coil is surrounded by an iron yoke, which with the end faces its open legs face the inner surface of the cylinder jacket via an air gap. at Excitation of the coil with alternating current creates a magnetic flux, its way from the yoke via the air gap, the cylinder jacket, leads the second air gap back into the yoke. Perpendicular to Because of the magnetic flux of force, eddy currents are induced in the cylinder jacket, which the jacket heat.

In this known device, the eddy current density in the cylinder jacket not evenly distributed over the entire axial width of the coil, but rather it is largest in the middle and falls off on both sides towards the coil ends. Accordingly, will the cylinder jacket is heated more strongly in the area of the coil center than in the vicinity of the coil ends. the Temperature distribution in the axial direction is uneven.

A measure for avoidance known from the German Auslegeschrift 1151724 already mentioned this disadvantage is that the coils are axially displaceable and by a Drive mechanism are moved back and forth approximately in the range of half a coil length. This measure but is very expensive and can also give rise to operational disruptions.

The invention allows the same goal to be achieved in a simpler manner, with no moving parts and no drive mechanism for the coil to reach. It consists in the fact that with a rotating drying cylinder with internally arranged electrical induction heating device of the type described above, the coil or the coils including the sequence of yokes surrounding them against the normal plane is inclined to the cylinder axis.

With this arrangement too, the eddy current density is unevenly distributed in the axial direction. The point with the greatest eddy current density, however, is not in a normal plane to the axis, but in a drying cylinder rotating in relation to the normal plane with inside
arranged, fixed induction heating device

Applicant:

Escher Wyss G. m. B. H., Ravensburg (Württ.)

Named as inventor:

Hans Heuschkel, Ravensburg (Württ.)

the coil plane inclined plane. In the inclination

! 5 direction opposite points with The highest eddy current density and thus the highest heat generation are therefore axially opposite to one another Shifted direction. Since the coil is arranged in a stationary manner, every point now reaches this area

a »of the circumferential cylinder jacket in the course of a Rotation to a point with the highest eddy current density ©, so that the differences are balanced out and the whole area is heated practically evenly.

The points of the coil lying opposite one another in the direction of inclination are preferably axially offset from one another by at least half the coil width. In the case of several coils arranged axially next to one another, the points of the coils opposite one another in the direction of inclination are advantageously axially offset from one another by at least half the coil pitch, but at most by three quarters of the coil pitch.
An exemplary embodiment of the subject matter of the invention is shown schematically in the drawing. It shows

1 shows an axial longitudinal section along the line I-I of FIG. 2 through part of a drying cylinder with the heating device according to the invention,

F i g. FIG. 2 shows a cross section along the line H-II of FIG

1 denotes the circumferential cylinder jacket, 2 one of its end walls, 3 denotes a stationary tube and 4 denotes a ball bearing placed on the tube and bearing the end wall 2. 5 and 6 are seals. The heating device according to the invention is carried by an inner tube 7 with a flange 8 inserted into the tube 3. The not

5 "indicated support for the other end of the cylinder jacket and the heater is designed substantially symmetrically thereto.

709 520/317

Claims (5)

237 The flange 8 carries an inner, stationary cylinder jacket 9, which leaves an annular space free between it and the circumferential cylinder jacket 1 and is provided on its outside with grooves 10 for receiving iron yokes 11 consisting of individual lamellae. The induction coils are designated by 12. There are several arranged axially next to each other within the cylinder jacket 1 concentrically to this stationary. They each have a number of turns of an electrical conductor 13, which is hollow for receiving a coolant, and running close to the inner surface of the cylinder jacket I. The induction coils 12 are excited with alternating current during operation and generate an alternating magnetic flux in the iron cylinder jacket 1. The yokes 11 distributed in a stationary manner on the circumference of the cylinder jacket 1 enclose the turns of the coils 12 from the inside and close the magnetic flux via air gaps 14 which are ao left free between the yokes 11 and the cylinder jacket 1. The coils 12 are inclined at an angle α relative to the normal plane to the cylinder axis. The opposite points in the direction of inclination are designated by A1 and A2. The points A1 and A2 are axially offset from one another by the distance a, which in the example shown is greater than half the coil width b. In the exemplary embodiment shown, the distance α is also greater than half the coil pitch t, but not greater than three quarters of the coil pitch t. The coil pitch t is advantageously chosen not to be greater than half the outer diameter D of the coil. In order to avoid that the magnetic flux in the yoke parts between adjacent coils is constantly compensated by the oppositely directed influence of the two coils, it is advantageous to excite the adjacent coils with alternating currents which are phase-shifted by 120 ° or more. In FIG. 1, for example, the course of the magnetic flux at 180 ° phase shift is indicated by arrows. The direction of rotation of the magnetic flux changes from coil to coil. Patent claims: 1. Rotating drying cylinder, e.g. B. for paper machines, with arranged inside, fixed induction heating device comprising at least one of iron yokes Has conductor coil, the open legs of the inner cylinder jacket via an air gap stand opposite and form with this a closed circuit for the induced magnetic flux, characterized in that the coil (12) including the sequence of those comprising it Yokes (11) is inclined relative to the normal plane to the cylinder axis. 2. Drying cylinder according to claim 1, characterized in that the points [A ₁ ; A ^ of the coil (12) are axially offset from one another by at least half the coil width (b). 3. Drying cylinder according to claim 1, with a plurality of axially juxtaposed bobbins, characterized in that the points (A ₁ ; A ₂ ) of the bobbins (12) opposite one another in the direction of inclination are axially at least half the bobbin pitch (i), but at most by Drel - quarter of the coil pitch (t) are offset from one another. 4. drying cylinder according to claim 3, characterized in that the coil pitch (r) at most half the outer diameter (D) of the coil (12). 5. drying cylinder according to claim 1, with a plurality of axially juxtaposed coils, characterized in that the alternating current of adjacent coils is phase shifted by at least 120 ° . Considered publications:
German interpretative document No. 1151724. 1 sheet of drawings 709 520/317 3.67 © Bundesdruckerei Berlin