Note: Descriptions are shown in the official language in which they were submitted.
20?760
Calender for Surface Treatment of Material Webs
The invention relates to a calender for treating material
webs, comprising at least one fixed roller which in
operation is fixedly supported in the pressing direction
and at least one movable roller which is mounted for free
movement in the pressing direction.
Such calenders are fairly well known. In particular, the
roller journals are mounted in elongate guides for free
movement in the pressing direction, so that they function
as movable rollers and are subject to limited movement in
these guides.
In this connection, problems arise from the fact that
considerable frictional forces can act in these guides
even to the extent of a more or less seizing effect. As a
result, for example with a vertically extending calender,
the expected pressing force in the roller gap of the fixed
roller can possibly be too high or too low on one side,
according to whether an increase or decrease of the
pressing force was executed. This leads to pressing forces
deviating from the desired value and/or to inclined press
force profiles in the roller gap, the latter occurring
since the friction forces are not always equally large in
the roller guides.
It has already been attempted many times to moderate the
effect of these frictional or seizing phenomena by
artificial shaking or moving of the entire roller assembly
in order to loosen the frictional forces. Also it has been
attempted to provide a remedy in that according to
circumstances a greater or smaller additional load is
applied by the movable roller until the desired pressing
forces are present at the fixed roller.
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In this way, it is partially achieved that with
approximately constant friction, the actual value of the
central line force or the central line force profile in
the roller gap on the fixed roller, taken as a measure of
the smoothing process, is brought to the desired value. In
many cases however it occurred that the friction was
increased until the guide seized as a direct result of the
mentioned techniques. In every case the line forces in the
roller gaps, which are located between the rubbing or
seizing roller and the moving roller experiencing the
additional loading, are incorrect which leads to a
considerable disturbance of the rolling process.
Therefore, the object of the invention consists in
providing a calender in which the mentioned friction and
seizing are avoided in a simple and reliable manner, or at
least in which their disadvantageous effect can be
mitigated without for example having to alter considerably
an existing calender.
This object is achieved according to the invention by an
arrangement for measuring the pressing forces on the fixed
roller 12, an arrangement for adjusting the fixed roller
12 in the pressing direction, an arrangement for comparing
the desired value of the pressing force with the actual
measured pressing force on the fixed roller, and a control
device for controlling the adjusting arrangement according
to the comparison between the actual and desired values
for achieving the desired pressing forces on the fixed
roller in the roller gap. The desired value of the
pressing force on the fixed roller is thus derived from
the components of the weight forces acting in the pressing
direction of the supporting parts movable across the fixed
roller in the pressing direction as well as the forces
impressed on the displaceable rollers.
This solution makes use of the idea of making the roller
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provided as such for operating as a fixed roller at least
selectively movable at the ends in the pressing direction,
in dependence upon the supporting forces measured at the
fixed roller, which are largely determined by the pressing
forces. The claimed principle operates generally both
upwardly and also downwardly (vertically extending
calender) and also in any other relative position of the
rollers, as for example horizontally where the calender is
horizontal. In this connection, a supplementary load can
be applied both from above and also from below or from
right or left.
With use of the invention, the disadvantage effect of the
frictional forces can be avoided not only on the adjusted
fixed roller but also in the roller gaps between the
adjusted fixed roller and the roller on which the harmful
frictional force appears.
According to the invention it is not necessary to know
which of the rollers is rubbing or seizing in its guides.
As the smallest unit, one fixed roller can be combined
with one movable roller.
Also movable rollers, which exert supplementary forces are
conceivable.
In conjunction with an upright calender, the fixed roller
can be provided either as the uppermost or as the
lowermost roller.
In conjunction with a horizontal calender, the fixed
roller can be provided either as the outermost right hand
or the outermost left hand roller.
It is also possible to provide the fixed roller in the
intermediate region of the calender.
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The fixed roller itself can expediently be constructed as
a deflecting equalization roller with fixed lateral
bearings of the roller sleeve (so-called NIPCO-K roller).
Also the fixed roller can be constructed as a deflecting
equalization roller with a roller sleeve movable in the
pressing direction over its entire length, which sleeve
can be fixed by a distance measuring arrangement at a
selectable position for operation in the pressing
direction (so-called NIPCO-F roller with position
control).
The movable roller, which can apply supplementary forces,
is advantageously conceivable as a deflecting equalization
roller with a roller sleeve movable in the pressing
direction.
For measuring the load on the rollers, load cells can be
employed or also hydraulic or pneumatic pressures can be
derived from the loading systems of the rollers.
For changing the position of the front ends of the
respective fixed roller, jacking devices, piston systems
or other mechanical arrangements can be used.
In conjunction with a fixed roller as deflecting
equalization roller with a roller sleeve movable in the
pressing direction over the entire length, which sleeve
can be fixed by means of a distance measuring arrangement
at a selectable position for operating in the pressing
direction, the said adjustment can be performed by
modifying the selectable position, e.g. by appropriate
inputs into a controller fixing the position of the roller
sleeve, or by modifying the position of the entire
deflecting equalization roller. Another possible technique
is to reduce artificially the clearance at the distance
measuring arrangement and thus to initiate readjustment.
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Readjustment of the position of the fixed roller towards
or away from the rubbing or seizing roller can be
separately automated at both roller ends in dependence
upon the actual-desired pressure force difference between
the fixed and movable rollers.
Further advantageous configurations appear from the
subsidiary claims.
The invention will now be described in the following in
more detail on the basis of exemplary embodiments
illustrated purely schematically in the drawings, in which:
Fig. la shows a schematic view of a calendar;
Fig. lb shows a schematic side view of the calendar
according to Fig. la;
Figs. 2a to 2e show various upright calendars and a
horizontal calendar; and
Figs. 3a and 3b show a two roller construction in
longitudinal and transverse section.
A calendar consists of a plurality of rollers arranged
behind one another which form a roller gap therebetween,
through which passes the paper web to be smoothed. With an
upright calendar according to Figs. la and lb, a lower
roller 12 and an upper roller 14 are provided with
intermediate rollers 16, 17 and 18 arranged therebetween.
A portion of the intermediate rollers is not illustrated
in Fig. la. Although either the upper or the lower roller
or even an intermediate roller can be provided as a
so-called fixed roller, in the example illustrated in Fig.
la, the lower roller 12 is constructed as a so-called
NIPCO roller having a roller sleeve 13 and a yoke 15. This
roller here represents a so-called fixed roller. These
NIPCO rollers can be constructed in various ways. To form
a so-called NIPCO-R roller, the roller sleeve 12 is itself
mounted laterally and bending equalization of the sleeve
takes place by means of intermediate supports which can be
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loaded using hydraulic oil. With the so-called NIPCO-F
roller, the roller sleeve is no longer laterally
supported, but rather the support takes place only over
the length of the roller sleeve on the yoke. Such a NIPCO
roller is a known deflection equalization roller.
On the roller sleeve 13 or on the yoke 15 is located a
position sensor 20 which is coupled to a position
controller 22. The deflection equalization supports
represented by the arrows 24 are supplied with hydraulic
oil in order to apply differential pressure on a linear
force profile in the roller gap 26 between the
intermediate roller 18 and the lower fixed roller 12
across the length of the roller. The control of the
hydraulic oil pressure is performed by means of an oil
pressure controller 28 coupled to the position controller.
The oil pressure at various positions of the roller gap
can be displayed graphically on a monitor via lines 30.
The position sensor 20 reports the actual position of the
NIPCO roller sleeve 13 to the position controller 22 which
continuously corrects the oil pressure of all zones in
such a manner that the NIPCO roller sleeve 13, and thus
the entire roller assembly assumes a definite horizontal
height position and maintains it. The entire roller
assembly floats as it were within quite narrow limits.
The rollers are guided by lateral journals 32 engaging in
vertical guides. The rollers normally lie on one another
in the vertical calender as a result of the weight of the
rollers themselves. However, also according to the arrows
34 a supplementary pressure can be applied laterally to
the upper roller 14. In this connection, the upper roller
14 can likewise be a NIPCO roller.
If for example seizure occurs on the right hand side in
the vertical guide of intermediate roller 17, this results
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in upward deflection of the roller sleeve 13 (NIPCO
sleeve) so that the position sensor 20 on the right hand
side in Fig. 1 experiences distancing in the vertical
direction between the associated sensor components. Thus,
on the seizing side the position sensor registers the
reduced loading as a small upward movement of the sleeve
and thus controls a correspondingly reduced oil pressure
on this side. The linear forces now applied by the
self-loading NIPCO roller uniformly increase from the side
where seizing occurs up to full loading on the opposite
side which is displayed as an inclined linear force
profile on the monitor via the lines 30. A differing
linear profile is illustrated by the arrows of differing
length in the region of the NIPCO roller in Fig. la.
According to the invention, the lower roller 12 arranged
as a fixed roller on the right hand side, i.e. on the side
of the seizure, is now moved upwardly in such manner that
again a uniform linear force profile across the length of
the roller is set according to the desired values. This
means that the actual fixed roller is adjustable in the
direction of the remaining rollers for re-regulation at
least at the ends.
It should also be mentioned that in the event of seizure
on the right hand side of the intermediate roller 17 the
conditions above this roller remain satisfactory, as
indicated by the arrows at that point in Fig. la. The
conditions beneath the seizure are brought back to the
desired condition by the regulation across the entire
length of the rollers.
Fig. 2 shows in schematic representation vertical
calenders in Figs. 2a to 2d and a horizontal calender in
Fig. 2e. In Fig. 2a, the rollers 14 and 16 are movable
rollers which are guided by means of guide components 17
in vertical guides 19. The lower roller 12 is here a fixed
roller.
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In Fig. 2b, the upper roller 14 is fixed in just the same
way as the lower roller 12, which however can here be
moved by a jacking unit 21 for active pressure force
application. Also this movement can be subject to seizure.
In Fig. 2c, the lower roller 12 is fixed, the upper roller
14 being movable vertically by a jacking unit 21 for
pressure force application.
Fig. 2d shows how the calender in Fig. 2b may have a lower
roller 12 movable by a jacking unit 21 as well as a fixed
intermediate roller 14 " .
In the horizontal calender of Fig. 2e, the right hand
outer roller 14' is fixed and the outer left hand roller
12' is movable by a jacking unit 21'. The intermediate
rollers 16' are likewise movable with guide components 12'
in a guide 19'.
In order to simplify this system, a measurement can be
performed separately at both ends of the fixed roller. In
this connection, it is irrelevant whether the loading is
applied by the self weight and an additional load above in
the vertical calender or is applied by force application
below. In each case it has to be ensured that, taking
account of the desired loading, the actual loading
appearing in the event of seizure possibly also on one
side is eliminated and brought back to the desired value
by slight movement of the fixed roller at the
corresponding end. The hydraulic or pneumatic pressures of
the pressure application system may for example serve as
measures of the loadings.
The possibility also exists of determining the respective
actual value in the region of the support of the fixed
roller using load cells and then performing regulation to
the desired value. For position change of the respective
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fixed roller, jacking devices, piston systems or other
mechanical arrangements are suitable.
Also measuring and positioning systems can occur in
combination, as for example the so-called "floating stack
principle" with position sensors in combination with self-
loading NIPCO rollers.
Readjustment of the position of the fixed roller towards
or away from the rubbing roller can be automated in
dependence upon the difference between the desired
Pressure deviation of the two extreme superimposed roller
gaps, separately at both roller ends. For the system, it
is not necessary to know which of the rollers is rubbing
or seizing in its guides.
Figs. 3a and 3b show a two roller system. This includes
two so-called NIPCO-F rollers. The roller sleeve 13 is
supported via pressure rams 42 on the yoke 15, where these
pressure rams can be selectively activated via a chamber
43 and an oil conduit 44, as shown by the arrows in Fig.
3a in the region of the pressure rams. The outer edge of
the roller sleeve 13 is supported via a bearing 40 on a
connecting member 38. This connecting member is movable
vertically on a guide of the yoke 15, as indicated by the
arrow in Fig. 3b. Thus it can be moved vertically relative
to the yoke 15 in dependence upon the pressure force
exerted by the pressure rams on the applied pressing
force, along the corresponding vertical guide surfaces 50.
The mentionded seizing can occur there as a result of the
increased friction. The movement of the roller sleeve 13
relative to the yoke 15 can be determined by a
displacement transducer 46. Here, the possibility exists
of compensating disharmony of the pressing forces in the
event of seizure occurring solely by use of simple
software control.
