BACKGROUND OF THE INVENTION
[0001] 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 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 substrate conveying speeds used.
[0002] Such rollers are generally used as supporting or guiding rollers in apparatuses for
treating web-type media, in which connection treatment may be understood to mean a
large number of operations such as coating, printing, subjecting to corona discharge,
exposure etc.
[0003] A roller of the indicated type is described in GB-A-1 056 372 which discloses a guide
roller assembly for a paper web handling machine.
[0004] A limited 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.
[0005] 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.
[0006] The present invention has as an object to provide a roller of the type concerned
which does not show said disadvantage and which allows for fast and easy changing
of the surface structure thereof.
[0007] 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.
[0008] 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.
[0009] Expediently such a seamless metal sleeve is a nickel sleeve having a thickness between
150 and 500 micrometer and in particular between 150 and 250 micrometer.
[0010] Such nickel sleeves are manufactured by the applicant and may be provided with any
desired circumference length and in any axial length.
[0011] 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.
[0012] 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.
[0013] This problem is solved according to the present invention by providing the surface
structure with a top layer of high wear resistance.
[0014] 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.
[0015] Of course many other materials may be mentioned in this respect; in above series
titanium-nitride is of particular importance.
[0016] 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 atmosphere.
[0017] 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.
[0018] 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 polytetrafluoroethylene coating layer in order to prevent wear of the roller
and damage to the substrate as much as possible.
[0019] 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.
[0020] In the embodiment described above, instead of a 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 superimposed on the structure of 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.
[0021] 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.
[0022] When the seamless metal sleeve is used measures may be taken to provide sufficient
rigidity to the sleeve used.
[0023] 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 material or a pressurized gas such as air.
[0024] As an example of a suitable foam plastic a polyurethane may be mentioned such as
polyurethane HHR® of Voss Chemie. This material is a semi-hard foam having a density
of approx. 26 kg/m³. Also a foam H 450® of Voss Chemie may be used; this is a polyurethane
foam which exhibits high pressure (5-6 kg/cm² overpressure) during hardening and has
a density of 450 kg/m³. When air is used to provide rigidity to a sleeve up to 1.3
kg/cm² overpressure may be used.
[0025] In another attractive embodiment, a sleeve can be carried in a clamping manner by
a supporting cylinder which is provided with axle means.
[0026] 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.
[0027] 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.
[0028] 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 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 thickness, this compressible roller will readily be sufficient
for forming the roller according to the invention.
[0029] 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 substrate
conveying speeds used, which is characterized in that the roller is a massive or thick-walled
metal roller and the surface structure is provided with a top layer of high wear resistance.
[0030] 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
of such roller with a top layer of high wear resistance.
[0031] 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.
[0032] In particular titanium nitride is found to offer valuable properties in terms of
hardness, wear resistance and appearance.
[0033] Also the top layer may comprise a metal layer such as a nickel-phosphorus or chromium
layer.
[0034] 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.
[0035] The invention finally relates to an apparatus for treating a moving web-type substrate
which comprises one or more substrate treatment units, substrate moving units and
one or more substrate supporting 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.
[0036] Such an apparatus for treating a moving web-type substrate 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 conveying 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 applied 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 THE DRAWINGS:
[0037] The invention will now be described with reference to the drawings, wherein:
Figures 1 to 4 show diagrammatically in partial 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 surface of a supporting cylinder; and
Figures 13 and 14 show the embodiment in which a non-supported sleeve is used.
[0038] In Figure 1a, 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 1b 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.
[0039] 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.
[0040] 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 of the application.
[0041] 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.
[0042] 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.
[0043] 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
engraving or laser beam engraving in metal.
[0044] Figures 6 and 7 indicate two very attractive embodiments of a surface structure 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.
[0045] 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.
[0046] 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 symmetrical 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
thicknesses. 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 abovementioned beam machining techniques using electron or laser beams
for forming the groove patterns.
[0047] 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 of the grooves can guarantee continuous
contact of the substrate with the material between the grooves 20.
[0048] Figure 9 shows a situation in which the surface 21 is provided with axially extending
grooves 22.
[0049] In practice this situation proves less adequate and, for certain groove dimensions,
may result in vibration of the substrate sheet.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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 cylinder
32 is provided with a number of radial openings 38 which debouch at the outside circumference
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 of 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.
[0054] 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 broken 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, 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.
[0055] 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.
[0056] The materials which may be applied with 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.
[0057] Of above materials in particular titanium nitride is useful. Said material may be
applied to the surface of a sleeve having a surface structure 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.
[0058] Other layers of high hardness can furthermore be deposited, for example, by electroplating
or by electrolessplating such as, for example, a chromium layer or a nickel-phosphorus
layer. As regards the hardness, a hardness which exceeds 500° Vickers will give good
results.
[0059] 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, 54 of the rings are constructed so that they
can be received in the stencil heads of the apparatus in, for example, a bayonet connection.
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 rings mounted on a
common axle; axial stress can be obtained if necessary by pushing the rings apart
on the axle.
[0060] 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.
[0061] 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 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.
[0062] 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.
1. 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 (3, 5, 6, 9)
as a result of which a predetermined volume of gas is enclosed between the substrate
which is in contact with the surface structure (3, 5, 6, 9) 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, characterized in that in that the roller comprises a seamless metal sleeve (52) at its surface which comes
into contact with the substrate and the surface structure (3, 5, 6, 9) is provided
at the surface of the sleeve (52).
2. Roller according to claim 1, characterized in that the sleeve (52) is a seamless nickel sleeve having a thickness between 150 and 500
micrometer, in particular between 150 and 250 micrometer.
3. Roller according to one or more of the preceding Claims, characterized in that the surface structure (3, 5, 6, 9) is provided with a top layer of high wear resistance.
4. Roller according to Claim 3, characterized in that the 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.
5. Roller according to Claim 3, characterized in that the top layer comprises a layer of a metal of high wear resistance and hardness such
as a nickel-phosphorus layer or a chromium layer.
6. Roller according to Claim 3, characterized in that the top layer comprises a layer of polytetrafluoroethylene.
7. Roller according to one or more of the Claims 1-6, characterized in that the sleeve (52) is mounted between two fixed end rings or flanges (50; 51).
8. Roller according to Claim 7, characterized in that the sleeve (52) is a sleeve provided with perforations.
9. Roller according to Claims 7 or 8, characterized in that means (57) are provided inside the sleeve (52) for establishing a predetermined pneumatic
pressure pattern in the axial direction.
10. Roller according to Claim 7, characterized in that the roller has been given rigidity by filling the interior of the sleeve (52) with
a material of low density.
11. Roller according to Claim 10, characterized in that the sleeve (52) has been filled with a material chosen from a cured foam plastic
and a pressurized gas.
12. Roller according to one or more of the Claims 1-6, characterized in that the sleeve (30) is carried in a clamping manner by a supporting cylinder (32) provided
with axle means (35, 36, 37).
13. 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 (3, 5, 6, 9)
as a result of which a predetermined volume of gas is enclosed between the substrate
which is in contact with the surface structure (3, 5, 6, 9) 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, characterized in that the roller is a massive or thick-walled metal roller and the surface structure (3,
5, 6, 9) is provided with a top layer of high wear resistance.
14. Roller according to Claim 13, characterized in that the 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.
15. Roller according to Claim 13, characterized in that the top layer comprises a layer of a metal of high wear resistance and hardness such
as a nickel-phosphorus layer or a chromium layer.
16. Roller according to Claim 13, characterized in that the top layer comprises a layer of polytetrafluoroethylene.
17. Apparatus for treating a moving web-type substrate and comprising one or more
substrate treatment units, substrate moving means and one or more substrate supporting
rollers, characterized in that the substrate supporting rollers have the form as described in one or more of Claims
1-16.