US4775773A
Expired / Lapsed
US
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Method and apparatus for controlling thickness of a web in a calendering nip
Assignee: Valmet Technologies Oy
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Filing: 1986-10-28
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Granted: 1988-10-04
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Expires: 2006-10-28
Abstract
Abstract Method and apparatus for controlling the thickness profile of a web passing through a calendering nip formed by two rolls, in which a variable magnetic flux is directed onto an outer surface on one of the rolls from a magnetic shoe device comprising a plurality of cores situated externally of the roll and over substantially the entire axial length thereof. Each core is spaced a discrete distance from the roll surface, with the magnetic flux acting to induce eddy currents along the surface of the roll, generating heat thereon. The roll diameter is changed over the length of the roll in a manner corresponding to the axial temperature profile of the roll, with the changes in diameter of the roll in turn determining the pressure profile across the calendering nip, and thereby determining the thickness profile of the web passing therethrough.
Inventors
- 👤 Matti Verkasalo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 15:04
CPC Classifications
D; D21; D21F; D21F7/00; D21F7/06; D21F5/00; D21F5/02; D21F5/022; D21F5/024; D21G; D21G1/00; D21G1/02; D21G1/0253; D21G1/028; H; H05; H05B; H05B6/00; H05B6/02; H05B6/06; H05B6/10; H05B6/14; H05B6/145
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
212 words
Calendering apparatus for calendering a web wherein the thickness profile of the web being calendered is controlled, comprising: a first calendering roll, a second calendering roll situated in nip-defining relationship with said first calendering roll, with the web passing through said nip between said two rolls, electromagnetic means for inducing eddy currents in said first roll and thereby heating the same, said electromagnetic means situated externally of said first roll and extending over substantially the entire axial length thereof, said electromagnetic means comprising a plurality of cores, each core being spaced a respective distance from the surface of said first roll, and means for changing diameter of said first roll over the axial length thereof, said changing means constituting means for adjusting said distance by which each core is spaced from said first roll surface independently of the distances by which the other cores are spaced from said first roll surface, whereby temperature profile over the axial length of said first roll is controlled to change the roll diameter over the roll length in a manner corresponding to the temperature profile thereof, the changes in diameter of said roll in turn determining pressure profile across the length of said calendering nip, and thereby determining the thickness profile of the web passing therethrough.
Claim 2
Dependent Claim
212 words
Calendering apparatus for calendering a web wherein the thickness profile of the web being calendered is controlled, comprising: a first calendering roll, a second calendering roll situated in nip-defining relationship with said first calendering roll, with the web passing through said nip between said two rolls, electromagnetic means for inducing eddy currents in said first roll and thereby heating the same, said electromagnetic means situated externally of said first roll and extending over substantially the entire axial length thereof, said electromagnetic means comprising a plurality of cores, each core being spaced a respective distance from the surface of said first roll, and means for changing diameter of said first roll over the axial length thereof, said changing means constituting means for adjusting said distance by which each core is spaced from said first roll surface independently of the distances by which the other cores are spaced from said first roll surface, whereby temperature profile over the axial length of said first roll is controlled to change the roll diameter over the roll length in a manner corresponding to the temperature profile thereof, the changes in diameter of said roll in turn determining pressure profile across the length of said calendering nip, and thereby determining the thickness profile of the web passing therethrough.
Claim 3
Dependent Claim
42 words
The apparatus of claim 1, additionally comprising means for supplying magnetizing current to said electromagnetic means, and means for adjusting frequency of said supplied magnetizing current, to thereby control depth of penetration of the heat into the roll below the surface thereof.
Claim 4
Dependent Claim
27 words
The apparatus of claim 2, wherein said electromagnetic means additionally comprise at least one magnetizing coil disposed about said cores and connected with said current supplying means.
Claim 5
Dependent Claim
16 words
The apparatus of claim 3, wherein a single coil is disposed about all of said cores.
Claim 6
Dependent Claim
16 words
The apparatus of claim 3, wherein a separate coil is disposed about each of said cores.
Claim 7
Dependent Claim
39 words
The apparatus of claim 3, wherein said distance adjusting means comprise a support arm affixed to each said core, and shaft means disposed on a frame of said apparatus, each support arm being pivotably mounted upon said shaft means.
Claim 8
Dependent Claim
65 words
The apparatus of claim 6, wherein said distance adjusting means additionally comprise motor means for adjusting position of said support arms and thereby adjusting position of said cores, said motor means being constituted by a plurality of eccentric cams, each eccentric cam rotatably contacting a respective support arm, and a plurality of stepping motors, each motor engaged with and adapted to rotate a respect cam.
Claim 9
Dependent Claim
31 words
The apparatus of claim 6, wherein each of said cores is substantially E-shaped with a middle and outer branches defining grooves therebetween, and said coil being situated in said defined groove.
Claim 10
Dependent Claim
43 words
The apparatus of claim 8, wherein said coil is substantially stationarily mounted within said grooves by at least one second support arm being mounted on the frame, such that position of said coil is independent of the adjustment of positions of said cores.
Claim 11
Dependent Claim
28 words
The apparatus of claim 4, wherein said coil is in the form of a hollow pipe, and additionally comprising means for conducting cooling fluid through said hollow pipe.
Claim 12
Dependent Claim
45 words
The apparatus of claim 1, additionally comprising means for detecting the temperature profile in at least one of the axial and radial directions of said roll, and connected with said distance adjusting means, with position of said cores being adjusted in response to detected temperature.
Claim 13
Dependent Claim
38 words
The apparatus of claim 11, additionally comprising means for pre-setting the axial temperature profile of said roll, and connected with said distance adjusting means, with position of said cores being adjusted in response to the pre-set temperature profile.
Claim 14
Dependent Claim
54 words
The apparatus of claim 6, wherein said distance adjusting means additionally comprise motor means for adjusting position of said support and thereby adjusting position of said cores, said motor means comprising a plurality of motors, each motor being engaged with a respective support arm and adapted to rotate the same about said shaft means.
Claim 15
Dependent Claim
211 words
In a calendering apparatus comprising at least two calendering rolls, a method for controlling thickness profile of a web passing through a nip formed by said rolls, comprising the steps of directing a variable magnetic flux into an outer surface of one of the rolls from a magnetic shoe device comprising a plurality of cores situated externally of the roll over substantially the entire axial length thereof, each core being spaced a respective distance from the roll surface, the magnetic flux acting to induce eddy currents along the surface of the roll and generating heat thereon, adjusting the magnitude of the distance by which each core is spaced from the roll surface independently of the distances by which the other cores are spaced from the roll surface, providing magnetizing current with a high frequency to ensure a low depth of penetration of the heat effect below the surface of the roll, whereby temperature profile over the axial length of the roll is controlled to change the roll diameter over the roll length in a manner corresponding to the temperature profile thereof, the changes in diameter of the roll in turn determing pressure profile across the length of the calendering nip, and thereby determining the thickness profile of the web passing therethrough.
Claim 16
Dependent Claim
211 words
In a calendering apparatus comprising at least two calendering rolls, a method for controlling thickness profile of a web passing through a nip formed by said rolls, comprising the steps of directing a variable magnetic flux into an outer surface of one of the rolls from a magnetic shoe device comprising a plurality of cores situated externally of the roll over substantially the entire axial length thereof, each core being spaced a respective distance from the roll surface, the magnetic flux acting to induce eddy currents along the surface of the roll and generating heat thereon, adjusting the magnitude of the distance by which each core is spaced from the roll surface independently of the distances by which the other cores are spaced from the roll surface, providing magnetizing current with a high frequency to ensure a low depth of penetration of the heat effect below the surface of the roll, whereby temperature profile over the axial length of the roll is controlled to change the roll diameter over the roll length in a manner corresponding to the temperature profile thereof, the changes in diameter of the roll in turn determing pressure profile across the length of the calendering nip, and thereby determining the thickness profile of the web passing therethrough.
Claim 17
Dependent Claim
15 words
The method of claim 14, wherein said distances are adjusted between 1 to 100 mm.
Claim 18
Dependent Claim
15 words
The method of claim 15, wherein said distances are adjusted between 1 to 30 mm.
Claim 19
Dependent Claim
18 words
The method of claim 14, additionally comprising adjusting the frequency of the current between 0.5 and 50 kHz.
Claim 20
Dependent Claim
15 words
The method of claim 17, wherein the frequency is adjusted between 1 to 30 kHz.
Claim 21
Dependent Claim
26 words
The method of claim 14, wherein said magnetizing current is provided through a common coil disposed about all said cores with from 1 to 5 windings.
Claim 22
Dependent Claim
21 words
The method of claim 14, wherein said magnetizing current is provided through a separate coil disposed about each of said cores.
Claim 23
Dependent Claim
30 words
The method of claim 14, wherein said magnetizing current is provided through a resonance circuit, and with a frequency above or below resonance frequency and at a safe distance therefrom.
Claim 24
Dependent Claim
24 words
The method of claim 21, additionally comprising measuring impedance of the resonance circuit, and adjusting the provided frequency in response to the measured impedance.
Claim 25
Dependent Claim
20 words
The method of claim 20, additionally comprising adjusting frequency of current supplied to each core through each of said coils.
Claim 26
Dependent Claim
24 words
The method of claim 21, additionally comprising adjusting the provided frequency based upon magnitude of the distance between the roll and each component core.
Claim 27
Dependent Claim
37 words
The method of claim 21, wherein the current is supplied through at least one frequency converter into at least one matching transformer, with said resonance circuit being connected to at least one secondary winding of said transformer.
Claim 28
Dependent Claim
37 words
The method of claim 25, additionally comprising setting at least one of the resonance frequency and supply voltage, by connecting said resonance circuit with tapping points on the secondary winding of said transformer through a change-over switch.
Claim 29
Dependent Claim
45 words
The method of claim 21, wherein the provided frequency is chosen above the resonance frequency, f r , within the range of 1.01f r and 1.15f r , or below the resonance frequency f r within the range of 0.85f f and 0.99f f .
Claim 30
Dependent Claim
16 words
The method of claim 27, additionally comprising choosing the resonance frequency between 2 and 35 kHz.
Claim 31
Dependent Claim
16 words
The method of claim 28, wherein the reference frequency is chosen between 20 and 30 kHz.
Claim 32
Dependent Claim
18 words
The method of claim 23, additionally comprising setting inductance of the resonance circuit between 10 and 250 μH.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-10-04 | 1992-04-04 | 1992-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-04 | 1996-04-04 | 1996-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-04 | 2000-04-04 | 2000-10-04 | $7700.00 | Window Closed / Lapsed |