COATING DEVICE FOR WEBS OF PAPER OR BOARD

DISPOSITIF DE COUCHAGE POUR BANDES DE PAPIER OU DE CARTON

English Abstract

COATING DEVICE FOR WEBS OF PAPER OR BOARD
ABSTRACT OF THE DISCLOSURE
The invention relates to a device for coating
traveling webs, in particular of paper or board, in which
the coating composition is applied to the web by a
rotating coating jacket at a coating nip formed between
the coating jacket and a counter-rotating backing roll.
In the region of the coating nip, the coating jacket is
guided over a slide shoe which extends parallel to the
nip and parallel to the backing roll, the slide shoe
being located within the coating jacket. The elide shoe
has an at least partially flat and/or convexly curved
slide surface at the coating nip and has a radius of
curvature of preferably more than 100 mm. The slide
surface further has an angular edge or projection portion
toward the downstream side, with respect to the rotation
direction of the coating jacket, which forms a deflection
in the coating jacket at a point where the coating jacket
separates from the backing roll.

Claims

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WHAT IS CLAIMED IS:
1. A device for coating a traveling web, in
particular web of paper or board, in which the coating
composition is carried by a rotating coating jacket to a
coating nip formed between the coating jacket and a
counter-rotating backing roll, through which the web
passes;
the coating jacket being guided over a slide
shoe which extends parallel to the coating nip and to the
backing roll and is located within the coating jacket and
urges the coating jacket against the backing roll;
the slide shoe having a slide surface which is
arranged at the coating nip and has a radius of curvature
of at least 100 mm, and a projecting portion of the slide
surface projects toward the backing roll and provides a
deflection is the coating jacket at a point where the
coating jacket separates from the backing roll.
2. A device as in claim 1, wherein the radius
of curvature of the slide surface is at least 300 mm.
3. A device as in claim 1, wherein said
projecting portion is at a downstream portion of said
slide shoe.
4. A device as in claim 3, wherein said
projecting portion is at a downstream edge of a surface
of said slide shoe facing said backing roll.
5. A device according to claim 4, wherein said
downstream said edge has a radius of curvature of 2 to 8
mm.

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6. A device as in claim 3, wherein said
projecting portion is at a downstream half of a surface
of said slide shoe facing said backing roll.
7. A device as in claim 1, wherein a contour
of the projecting portion of the slide surface drops
steeply with respect to the coating jacket and has a
radius of curvature of 2 to 8 mm.
8. A device according to claim 1, wherein the
projecting portion is at a steeply falling-off
downstream-side edge of the slide surface of the slide
shoe and extends at least 8 mm out of a support which
holds the slide shoe.
9. A device according to claim 8, wherein said
downstream side edge has a radius of curvature of 2 to 8
mm.
10. A device for coating a traveling web, in
particular a web of paper or board, in which the coating
composition is carried by a rotating coating jacket to
coating nip formed between the coating jacket and a
counter-rotating backing roll, through which the web
passes;
the coating jacket being guided over a slide
shoe which extends parallel to the coating nip and to the
backing roll and is located within the coating jacket and
urges the coating jacket against the backing roll;
wherein a radius of curvature of the slide shoe
at an upstream side (k2) is at least 25 mm and at a
downstream side (k2) at most 20 mm, and the slide shoe
thereby provides a point of deflection for the coating

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jacket where the coating jacket separates from the
backing roll.
11. A device according to claim 10, wherein
said downstream-side radius is 2-8 mm.
12. A device according to claim 11, wherein
the ratio of the upstream-side radius (k1) to the
downstream-side radius (k2) is at least 4:1.
13. A device according to claim 10, wherein
the ratio of the upstream-side radius (k,) to the
downstream-side radius (k2) is at least 4:1.
14. A device for coating a traveling web, in
particular a web of paper or board, in which the coating
composition is carried by a rotating coating jacket to a
coating nip formed between the coating jacket and a
counter-rotating backing roll, through which the web
passes;
the coating jacket being guided over a slide
shoe which extends parallel to the coating nip and to the
backing roll and is located within the coating jacket and
urges the coating jacket against the backing roll;
wherein:
the slide shoe has a first slide surface at its
upstream side, with respect to the movement direction of
the coating jacket;
the slide shoe has a second slide surface
downstream from said first slide surface in the form of a
projection having an upstream-side radius of curvature
(r1) of at least 20 mm;

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on the downstream side, the radius of curvature
of said second slide surface (r2) is 2 to 8 mm; and
the slide shoe has a third slide surface on its
downstream side.
15. A device according to claim 14, wherein
said upstream radius of curvature (r1) is at least 25 mm.
16. A device according to claim 14, wherein
said downtream radius of curvature (r2) is 2 to 8 mm.
17. A device according to any one of claims 1,
10 and 14, further comprising a plurality of the
additional slide shoes distributed over the inner
circumference of the coating jacket.
18. A device according to claim 17, wherein
that the distance apart of the additional slide shoes
along the coating jacket is at least 40 mm.
19. A device according to claim 1, wherein the
coating jacket is mounted on a pair of end clamping disks
and is driven by them for rotary movement approximately
on a circular path.
20. A device according to claim 1, wherein the
slide shoe comprises a pressure piston.

Description

2~9~677
COATING DEVICE FOR WEBS OF PAPER OR BOARD
BACKGROUND OF THE INVENTION
The invention relates to a device for coating
traveling web~, in particular of paper or board, in which
the coating composition is applied to the web by a
rotating coating jacket at a coating nip formed between
the coating jacket and a counter-rotating backing roll.
In the region of the coating nip, the coating jacket is
guided over a slide shoe which extends parallel to the
nip and parallel to the backing roll, the slide shoe
being located within the coating jacket.
The invention relates more particularly to
improvements in the slide shoe.
A coating device for coating webs of paper or
board is known from Federal Republic of Germany 41 00 771
A1. In that device, a rigid slide shoe is held on a
fixed, beam-shaped support which extends parallel to the
backing roll and to the coating nip. The slide shoe is
adjusted to the coating nip via pressure from a pressure
hose. The con6truction is such that the coating jacket
is guided around two drive rolls so as to rotate in a
trough. In this case, enormous problems in sealing arise
in order to block off the inside of the coating jacket,
and thus the ~urfaces of the drive rolls not wrapped by
the coating jacket, to prevent entry of the coating
COmpOsitlOn.
It would be desirable to develop a coating
device that can avoid those problems.
It is also desirable for the coating device to
dependably avoid skip coating or an "orange-peel" effect.

2096677
SUMMARY OF THE INVENTION
The above and other objects are achieved in
accordance with the invention by the features disclosed
; and claimed herein.
According to an aspect of the invention, the
slide shoe has at least partially flat and/or convexly
curved slide surface at the coating nip and has a radius
of curvature of at least about 100 mm, and preferably at
least about 300 mm. The slide surface further has an
angular edge or projection portion toward the downstream
side, with respect to the rotation direction of the
coating jacket, which forms a deflection in the coating
jacket at a point where the coating jacket separate6 from
the backing roll.
According to further aspects of the invention,
advantageous radii of curvature and other measurements,
for portions of the angular edge or projecting portion of
the slide shoe, are also disclosed and claimed herein.
Other features and advantages of the present
invention will become apparent from the following
description of the invention which refers to the
accompanying drawings.
BRIEF DESCRIPTION OF THE ~RA~INGS
An embodiment of the invention will be
described in detail below with reference to the figures,
in which:
Fig. 1 diagrammatically shows a cross-section
through a device in accordance with the invention;
Fig. 2 is a cross-section through the coating
jacket and its support;
Fig. 3 is an axial section corresponding to
Fig. 2;
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2096677
Fig. 4 is a partial cross-sectional view of a
variant of the slide shoe; and
Fig. 5 shows a further variant of the slide
shoe, in cross-section.
DETAI~ED DESCRIPTION OF AN EMB~PI~ENT OF THE INVENTION
The backing roll 3 conducts the web of paper W
through the coating nip formed between the coating jacket
1 or its supporting slide shoes 4 and the backing roll 3.
In this connection, the ho~e rotates through the coating
composition which i8 contained in a trough 14 and the
slide shoe 4 is held by a support 2. The support 2 can
preferably also have slide shoes 9, 10 and 11 distributed
over the remaining circumference of the coating jacket.
The slide shoe 4 is guided and held in the
support 2 in the manner of a pressure piston in a
pressure chamber 5 to which liquid is fed under pressure
via hole~ 28 and conduits 29. Excess pressure agent and
lubricant can be led away at the bottom shoe 10 via a
conduit 30 (for instance, by being pumped off by a pump).
Coating jacket 1 is held on end clamping disks
12 which serve also for driving the coating jacket, for
instance, via a gear rim 13. The stub shafts 23 are
mounted in tapered roller bearings 15. End tabs of the
press jacket 1 are fastened to the clamping disks 12 by
mean6 of end disks 20 and screws 22.
The coating jacket 1 is separated abruptly from
the backing roll 3 by the edge on the downstream side
(with respect to the web movement direction) of the slide
surface 17 of the slide shoe 4. For this purpose, the
radius of curvature of the slide surface 17 of the slide
shoe 4 is greater than 100 mm, preferably more than 300
mm. The edge on the downstream side, which extends
I

`2~96677
parallol to th~ bac~g xoll ~nd to th~ coating nip wh~rr~
the coating mat~rial ~s transferred to ehe web, extend3
nt le~st 8 mm abo~e the guide ~urfa~e in -he pres~ure
chamber S which guide~ ~he side ~urface 24 on the
s downstre~m ~ide o' thc ~llde sh~e ~.
In order to protect against scraping of the
cL~mpi~g dis~ 12 on the s~pport ~, the l~tt~r h~
emergency-travel bearin~ ~ur~ace~ 13, for iD6tance of
bearing metal or bron~e. The liquid c~nduits 25 a~d 30
are e~tende~ ~utward through end pins 33 of the support
z. A s~al 21 ls also provi~ed ror sealing the coAting
compo~ition trough 14 at the stub shaft6 23. The
bear~ngs 1~ are supported vla ~rac~ets 18 on the coa~ir.~
eompo62ition trough la. 2ther C~pports are, howe~rer, al60
po~ le.
Fig. ~ ~ho~e a variant in which the sllde shoe
4' has in it~ central region a ~no~-~haped or ridge-
~hapod pro~er~tio~ 31 w~ich extend6 parallQl to th~
coating nip and slide shoe. The projection ~ay ha~e a
2 0 r~diQ~ of c~r~rclturo rl -- in the plcl~o of the draw;ns~
of about 20 to 50 mm, and preferabl~ of at mo~ ~bout
20 mm. It p~eferably extends abcut 20 to 40 ~m f ro~ the
slide surface ~e~ Fig. 2~ of the slide shoe 4 r . The
down~tream-side rad~u~ o~ curvature r2 ca~ be mu~h
6malle~ and i8 preferably about 2 to 8 mm. By thi~
~tructure, the course o~ the coating jac~et 1 is ~mparted
a rola~ivel~ c~arp d~lectio~ a~ tho pro~oction 31 ~o
that an abrupt separation from the backing ro~l 3 takes
place hcr~. Furth~r slid~ eurfac~c 33 and 34 ar~
provLded at the ~eginni~g and e~d o~ the sl1de shoe 4',
bu~ thoy nood not noce~arlly bo pro~ent~ for ox~mple,
the fi~6t slide ~urface 34 on ~he upst~eam side in
p~rticul~r can be ~mitted.
.

2096677
In aecord~nce with FLg~ 5, the dc~n~tre~m-~ido
xadiu6 of cur~atu~e k2 of the support 6hoe ~ o~ the
projection 3~ v~r~ ~ma1 and i8 pr~erably ab~ut 1 to
20 mm, and m~re pref~rably about 2 to 8 mm. The
upstxeam-s$~e xad~us of curvature ~ f 6 at least 4 nimee
a~ great and i~ at le~st abQut 20 ~nm and preferably at
least about 60 ~n. The~e value~ can apply al80 tO the
projoction 31 o~ ~ig. 4.
Although the pregent irlvention ha6 ~een
~cribod in r~lation to particuIar o~ ~ont~ thoroo,
many othe~ ~axiatio~6 and modi~ication6 and other uses
will ~como appar~nt to tho-o ~kill~d in tho ~t. It i6
preferred, therefore, that the pre~ent in~ention be
limitcd not by the ~pecific di~looure heroin, but onl~
: 15 by the appended cla~ms.
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