Note: Descriptions are shown in the official language in which they were submitted.
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Short title: Supporting or guiding roller and apparatus
provided with one or more of such rollers.
BACKGROUND OF THE INVENTION
The present invention relates to a roller for use in the
guiding and/or supporting of a moving web-type substrate, in
an apparatus for treatment thereof wherein the surface of
said roller which comes into contact with the substrate is
provided with a surface structure as a result of which a
predetermined volume of gas is enclosed between the sub-
strate which is in contact with the surface structure and
the roller and the structure is given a form such that said
volume of gas remains essentially the same at the substrate
conveying speeds used.
Such rollers are generally used as supporting or
guiding rollers in apparatuses for trea-ting web-type media,
in which connection treatment may be understood to mean a
large number of operations such as coating, printing, sub-
jecting to corona discharge, exposure etc.
A roller of the indicated type is described in
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GB-A-l 056 372 which discloses a guide roller assembly for
a paper web handling machine.
A limitecl number of surface structures is described
which all serve to prevent the build up of an air cushion
between the moving paper web and the guiding roller in the
handling machine concerned.
Said known guide roller has as a disadvantage that a
large number of different rollers is needed when the
handling machine is intended for various purposes and/or
various substrates.
SUMMARY OF THE INVENTION.
The present invention has as an object to provide a
roller of the type concerned which does not sh~w said dis-
advantage and which allows for fast and easy changing of
the surface structure thereof.
Said roller is thereto characterized in that the roller
comprises a seamless metal sleeve at its surface which
comes into contact with the substrate and the surface
structure is provided at the surface of the sleeve.
By providing a roller of which the surface is formed by
a separate seamless metal sleeve a rapid change of surface
structure is possible as will be explained later in detail.
Expediently such a seamless metal sleeve is a nickel
sleeve having a thickness between 150 and 500 micrometer
25 and in particular between 150 and 250 micrometer.
Such nickel sleeves are manufactured by the applicant
and may be provided with any desired circumference length
and in any axial length.
The surface of such sleeves may be given any desired
surface structure which may be applied in a plurality of
ways as will be explained in the drawings.
With a roller of the type described a rapid wear of the
surface structure may be observed, for example when guiding
or supporting paper materials having great roughness or
high filler percentages.
This problem is solved according to the present
invention by providing the surface structure with a top
layer of high wear resistance.
In particular such a top layer comprises a wear
resistant material chosen from:
- nitrides such as of titanium or boron,
- carbides such as of silicon, boron, tungsten and
titanium,
- glass and quartz.
Of course many other materials may be mentioned in this
respect; in above series titanium-nitride is of particular
importance.
It is a very hard, wear-resistant material having a
very attractive light yellow colour; it may very
effectively apply to a surface by sputtering techniques
such as sputtering of TiN or reactive sputtering of Ti in
a nitrogen containing ati-nosphere.
In order to prevent damage to the substrate as much as
possible, it is attractive to round off the parts of the
surface structure of the roller which come into contact
with the substrate.
With very great advantage, the surface structure of the
roller according to the invention is provided with a top
layer having high wear resistance, such as a nickel-
phosphorus layer or chromium layer; the surface structure
may also, for example, be provided with a polytetrafluoro-
ethylene coating layer in order to prevent wear of the
roller and damage to the substrate as much as possible.
In one attractive embodiment, the sleeve incorporated
in the roller is mounted under axial stress between two end
rings or flanges mounted on a shaft. Such a roller has the
advantage that the weight thereof can be extremely low, as
a result of which the roller will readily start to rotate
concomitantly with the substrate to be supported or guided.
In the embodiment described a~ove, instead of a
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continuous sleeve, use may also be made of a sleeve
provided with perforations such as, for example, a metal
rotary screen-printing stencil. Such a stencil may be
composed, for example, of nickel and have a fineness of
250-500 mesh (= holes per linear inch), although lower or
higher finenesses are possible. The thickness may vary
between 100 and 250 micrometers or thicker. If such a
perforated sleeve is used, the surface structure may
comprise a separately provided structure which is super-
imposed on the structure o- the perforation pattern of
the sleeve. In certain cases, the structure of the
perforation pattern itself will also be sufficient to
guarantee that the sheet-type substrate always remains in
contact with the surface of the sleeve.
In an attractive embodiment, means such as, for
example, a labyrinth of partitions are present inside the
sleeve in order to make it possible to adjust an axially
extending pressure profile inside the perforated sleeve in
a predetermined manner. Such a labyrinth structure may
optionally rotate concomitantly with the perforated sleeve;
the pressure profile may be in the overpressure range and
(possibly partly), in the underpressure range. Regulation
of the pressure inside the perforated sleeve makes possible
a further perfecting of the substrate contact behaviour, as
a result of which even locally occurring imperfections in
the substrate contact can be remedied.
When the seamless metal sleeve is used measures may be
taken to provide sufficient rigidity to the sleeve used.
One general approach is to mount the sleeve, either
unperforated or perforated between two end rings or flanges
under axial stress. This will provide a basic rigidity to
such sleeve or screen which is sufficient for low contact
pressure of the guided web. If higher pressures are to be
taken a sleeve, in this case having no perforations, may
have rigidity by a filling in the interior thereof of a
material of low density such as a cured foam plastic
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material or a pressurized gas such as air.
As an example of a suitable foam plastic a poly-
urethane may be mentioned such as polyurethane HH ~ of Voss
Chemie. This material is d semi-hard foam having a density
of approx. 26 kg~m3. Also a Eoam H 450~of Voss Chemie
may be used; this is a polyurethane foam which exhibits
high pressure (5-6 kg/cm overpressure) during hardening
and has a density of 450 kg/m . When air is used -to provide
rigidity to a sleeve up to 1.3 kg/cm overpressure may be
used.
In another attractive embodiment, a sleeve can be
carried in a clamping manner by a supporting cylinder which
is provided with axle means.
In connection with the lastmentioned embodiment of the
roller, reference is made to European Patent Specification
0,160,341 of Stork Screens. Said patent specification
describes a method for manufacturing a screen roller in
which a thin-walled seamless cylindrical screen is pushed
around the surface of a hollow thick-walled or solid
roller. To mount the screen around the circumference of the
supporting cylinder, the perforations of the screen are
sealed, after which the diameter of the screen is
temporarily increased with the aid of, for example, air
pressure, with the result that the screen can be pushed
around the roller.
To manufacture the roller according to the present
invention, in which process the roller is formed by a
supporting cylinder around which a seamless metal sleeve is
pushed in a clamping manner, the technique described in
said patent specification may also be used.
Another form of a supporting roller is a so-called
compressible stretching roller such as is described in the
non-prepublished Dutch Patent Application No. 88 00 781 of
Stork Screens. In said document, a supporting roller is
described with, at the surface, a continuous coating which
can be pressed in. By pushing a sleeve over a short
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distance around the coating and feeding a medium under
pressure, for example gas, between the sleeve and the
coating, this latter can be pressed in and the possibility
of pushing the entire sleeve around the coating.
Especially in the case of a sleeve having large wall thick-
ness, this compressible roller will readily be sufficient
for forming the roller according to the invention.
The invention also relates to a roller for use in the
guiding and/or supporting of a moving web-type substrate,
in an apparatus for treatment thereof wherein the surface
of the roller which comes into contact with the substrate
is provided with a surface structure as a result of which a
predetermined volume of gas is enclosed between the
-substrate which is in contact with the surface structure
and the roller and the structure is given a form such that
said volume of gas remains essentially the same at the sub-
strate conveying speeds used, which is characterized in
that the roller is a massive or thic]c-walled metal roller
and the surface structure is provided with a top layer of
high wear resistance.
In order to protect the surface structure of the
inventive roller against influences of abrasive materials
it has proved very advantageous to provide the surface
structure oE such roller with a top layer of high wear
resistance.
Such top layer may thereto comprise various
materials of which may be mentioned:
- nitrides such as titanium and boron nitride,
- carbides such as silicon, boron, tungsten and titanium
nitride,
- glass and quartz.
In particular titanium nitride is found to offer
valuable properties in terms of hardness, wear resistance
and appearance.
Also the top layer may comprise a metal layer such as
a nic]~el-phosphorus or chromium layer.
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Attractive is also a polytetrafluoroethylene layer
having a very low coefficient of friction; in this
respect also mixed ceramic-polytetrafluoroethylene layers
may be mentioned. The latter layers may expediently be
applied by a plasma spraying process.
The invention finally relates to an appara-tus for
treating a moving web-type substrate which comprises one or
more substrate treatment units, substrate moving units and
one or more substrate suppor-ting rollers, such an apparatus
being characterized in that the substrate supporting
rollers have the form as described above for a roller
according to the invention.
Such an apparatus for treating a moving web-type sub-
strate may, for example, be an apparatus for applying a
coating to a web-type substrate. As an example, mention may
be made of the application of an emulsion to a web-type
substrate such as a polyester substrate. The uniformity of
such a coating is of the greatest importance; constructing
the substrate supporting or guiding rollers according to
the invention in the coating apparatus guarantees, as
regards the sonveying section of the apparatus, that a
disadvantageous effect is not exerted on the substrate or
the coating applied to the substrate. Expediently, such an
apparatus is, for example, a rotary screen-printing
apparatus in which a uniform coating is appIied to, for
example, a polyester web with the aid of a seamless nickel
screen-printing stencil. Apart from the abovementioned
components of such an apparatus, it may also comprise, for
example, drying units in order to be able to subject the
layer or layers applied to a drying operation.
BRIEF DESCRIPTION OF TI~E DRAWINGS:
The invention will now be described with reference to
the drawings, wherein:
Figures 1 to 4 show diagrammatically in partial
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section and plan view a number of possible forms of a
surface structure of the roller;
Figure 5 shows a special form of a component of the
surface structure of a roller;
Figures 6 and 7 show a special form of a surface
structure which serves to make possible gas removal to the
ends of the roller;
Figures 8 and 9 show surface structures of divergent
efficiency;
Figures 10 and 11 show a surface structure which is
obtained by electrolytically depositing metal;
Figure 12 shows the principle of fitting a metallic
seamless cylindrical sleeve around the surf~ce of a
supporting cylinder; and
Figures 13 and 14 show the embodiment in which a non-
supported sleeve is used.
In Figure la, 1 indicates in partial section the body
of a roller or a metallic seamless sleeve, while 2 and 3
indicate the surface structure situated on the surface of
the roller or sleeve. From Figure lb it can be seen in
partial plan view that the surface structure comprises
spherules 2 with gaps 3, while the spherules are arranged
in equilateral triangle structure.
It is pointed out that the regular structure shown
here is not a necessity; a rough nature may also be given
to the surface of a roller or sleeve by, for example,
abrasion, sandblasting, beadblasting or shot peening, in
which case the peak-to-valley height will expediently have
a value Ra of up to 12.5 micrometer. A normal smooth
roller or a metal sleeve obtained by electrodeposition such
as a nickel sleeve will have a peak-to-valley height
Ra < 0.2 micrometer.
Figure 2a indicates that cavities 5 have been formed
in the roller body or sleeve body 4 by etching. It will be
possible for the width and depth and also the pattern
configuration of the grooves 5 to be chosen as a function
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of the application.
Figure 3 indicates that the roller body or sleeve body
7 is provided with a structure of arbitrarily arranged
spherules 6, such spherules being joined to the surface of
the roller or sleeve by cementing. It is pointed out that,
with such an embodiment, a calibration operation should
additionally be carried out subsequent to forming the
surface structure layer in order to provide, in this way,
the roller with true running; the calibration also serves
to guarantee that all the spherular components have one
and the same height above the surface of the roller or
sleeve. Figure 3b indicates the situation in Figure 3a in
plan view, as was also the case in Figure 2b in relation to
Figure 2a.
In Figure 4a, 9 indicates a groove in the surface of a
roller or sleeve, the elevations between the grooves being
indicated by 8. From Figure 4b it is evident that the
grooves extend helically in the longitudinal direction of
the roller, assuming that the axial direction of the roller
extends in the direction of the arrow which is indicated in
Figure 4b. Incidentally, it is pointed out that in all the
figures given above, an axial direction of the roller or
sleeve is assumed which is identical to the direction of
the arrow in Figure 4b. Figure 4c indicates that the tips of
the material 8 between the grooves 9 are rounded off by
additional operational steps such as bright pickling,
latching, etching or the like.
Figure 5 indicates that a surface structure can be
obtained by machining, with a milling wheel, the surface of
the roller or a sleeve to be used, as a result of which
recesses 10 are obtained which are connected to one another
by means of channels 10', with the result that a
possibility of mutually displacing gas between the recesses
is nevertheless ensured. Apart from the abovementioned
mechanical forming of the recesses, the forming of recesses
can, of course, also be conceived by means of electron beam
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engraving or laser beam engraving in metal.
Figures 6 and 7 indicate two very attractive
embodiments of a surface struc-ture of a roller or sleeve in
which the structures are formed as mirror images with
respect to each other around the centre of a roller. In
Figure 6, a groove pattern 13 is shown in part 11 on the
right-hand side of the centre, the pattern 13 being
helically arranged in such a manner that, on rotating a
roller in the correct direction, a gas transport takes
place to the right in the drawing. At the left-hand side of
the centre of the roller in part 12, the groove pattern is
oppositely directed, as a result of which, with the same
rotation, a gas transport can occur to the left.
In Figure 7 the same situation is indicated in which a
pattern of overlapping opposite thread is present in each
of the two parts on either side of the centre of the
roller. In such a situation, a groove width gradient can be
used, as a result of which, for example, the resistance to
displacement in the grooves decreases from left to right
for one of the threads and from right to left for the other
thread.
Such embodiments arranged in mirror form appear to be
very advantageous if, apart from a controlled pressure
build-up of the gas, there has to be a requirement for
effects which have to promote positional accuracy of the
substrate during movement thereof. As a result of a symme-
trical air displacement starting from the centre of the
roller, an improved positional accuracy of the substrate
with respect to the roller is obtained, in which case a
certain flattening side effect on the substrate sheet is
also observed, and this is extremely desirable for specific
materials and low sheet thic]cnesses. To form such patterns,
use may advantageously be made of etching techniques using
photoresist patterns, it also being possible for a groove
depth variation to be achieved by using special techniques.
Of course, in that case, recourse may also be made to the
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abovementioned beam machinlng techniques using electron or
laser beams for forming the groove patterns.
Figure 8 shows a surface structure of a roller 19 in
which circumferential grooves 20 are present. In this case
no displacement of air takes place towards the ends of the
roller; nevertheless, suitable dimensioning oE -the grooves
can guarantee continuous contact of the substrate with the
material between the grooves 20.
Figure 9 shows a situation in which the surface 21 is
provided with axially extending grooves 22.
In practice this situation proves less adequate and,
for certain groove dimensions, may result in vibration of
the substrate sheet.
Figures 10 and 11 indicate that a surface structure
can be obtained on a roller or sleeve with the aid of
electroplating techniques. Figure 10 indicates a roller
body or sleeve body 23, while 25 indicates an electroplated
metal deposit which has grown between photoresist regions
which were previously situated at the positions which are
now indicated by 24.
In Figure 11 an electroplated deposit 27 is formed on
a roller body or sleeve body 26 with an overhang 28, the
overhang having taken place over photoresist areas which
were situated at the positions indicated by 29.
Regulation of the airflow over the surface of the
roller or sleeve can suitably be taken into account by
choice of the upward growth/overhang ratio.
Figure 12 indicates diagrammatically how a sleeve 30
can be fitted around the surface of a roller 32 in a manner
such as is indicated in the abovementioned European Patent
Specification 0,160,341. In this case the roller is a
thick-walled hollow roller which is provided with
supporting axles 35 and 36 which have disc-type sections 37
which are pushed in a clamping manner into the ends of the
cylinder. The disc-type sections 37 rest against a collar
at the inside of the cylinder. One of the ends of the
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cylinder 32 is provided with a number of radial openings 38
which debouch at the outside circumEerence of the cylinder
and which are in communication with axially directed
channels 40 which are provided in the left-hand disc-type
section 37. Each of the channels 40 has a blind end or a
sealing plug 39; the other end oE the channels 40 is in
communication with the internal space 33 of the supporting
cylinder 32. The disc-type section 37 at the right-hand
side of the cylinder has at least one axially directed
channel 34 which is, on the one hand, in communication with
the space 33 and, on the other hand, with a connecting
nipple 41. The nipple 41 can be connected via a hose, which
is not shown, with a source, which is equally not depicted,
of the medium, usually compressed air. In order to fit the
sleeve 30 on the roller 32, the outermost section of the
cylinder 32 is chamfered, with the result that the sleeve
30 can be pushed over the chamfered part up to the openings
38. A pressurized medium is then fed into the space 33 via
the connection 41 and the channel 34 in a manner such that
the sleeve 30 is expanded elastically and, as a result, can
be pushed further over the supporting cylinder 32. In this
connection, the pressurized medium has the double function
of expanding the sleeve 30 somewhat and at the same time
acting as a lubricant in pushing the sleeve over the
supporting cylinder.
After completing the pushing-on operation, a
connection to the source of pressurized medium can be
broken and this medium leaks away, after which the sleeve
30 is situated on the supporting cylinder 32 in a clamping
manner. In Figure 12, a bro]cen line on the surface of the
supporting cylinder 32 indicates that the outside of the
cylinder is chromium-plated or covered with a thin
chromium-plated cuff which serves to provide the surface of
such a cylinder with adequate wear resistance, with the
result that it can be used many times. As regards the
rollers or sleeves to be used according to the invention,
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it may be pointed out that, in general, a high degree of
wear resistance will be aimed at which, on the one hand,
can be achieved by using a wear-resistant material with low
coefficient of friction such as polytetrafuoroethylene; on
the other hand a wear-resistant material may also be used
with a high hardness.
Ion implantation -technique, CVD (chemical vapour
deposition) and PVD (physical vapour deposition) may also
be used to provide wear-resistant properties at the surface
of a roller or sleeve.
The materials which may be applied wi-th use of above
techniques can be various. Mention can be made of:
- nitrides such as of titanium and boron,
- carbides such as of silicon, boron, -tungsten and
titanium,
- quartz and glass.
Of above materials in particular titanium nitride is
useful. Said material may be applied to the surface of a
sleeve having a surface s-tructure by sputtering techniques.
Titanium nitride may be sputtered directly from a titanium
nitride target or formed by reactive sputtering of titanium
from a titanium target in a nitrogen-gas comprising
atmosphere.
Other layers of high hardness can furthermore be
deposited, for example, by electroplating or by electro-
lessplating such as, for example, a chromium layer or a
nickel-phosphorus layer. As regards the hardness, a hard-
ness which exceeds 500 Vickers will give good results.
Figure 13 shows the situation where a roller according
to the invention comprises a sleeve 52 received between end
rings, which sleeve may be a closed sleeve or a sleeve
having perforations which is provided with an additional
surface structure. The end rings are in this case stencil
end rings 50 such as are used, for example, in rotary
screen-printing machines. The ends 53, 5~ of the rings are
constructed so that they can be received in the stencil
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heads of the apparatus in, for example, a bayonet connec-
tion. The rings can exert an axial stress in a machine on
the sleeve 52; that is not, however, necessary. The end
rings 50 and 51 may also be replaced by end rinys mounted
on a common axle; axia] stress can be obtained if necessary
by pushing the rings apart on the axle.
As indicated before inside the sleeve 52 a filling of
a low density material may be provided such as a plastic
material, in particular a cured foam plastic or a
pressurized gas to impart rigidity to the roller.
Figure 14 shows the situation where the sleeve 52 is a
perforated sleeve such as a rotary screen-printing stencil.
The axle 56 in this case carries a labyrinth 57 in order to
achieve a predetermined pneumatic pressure profile over the
lS length of the sleeve. By varying the labyrinth partition
spacings and suitably arranging gas supply and/or removal
openings, a suitable axial profile comprising underpressure
and/of overpressure locations can be established.
An underpressure may be desirable in cases of high web
transportation speeds at low web tension; a slight degree
of overpressure may be expedient when working at low web
speeds at high web tension.
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