Note: Descriptions are shown in the official language in which they were submitted.
CA 02535954 2006-02-15
RELEASE-AGENT APPLICATOR
The invention relates to a release-agent applicator for the belt of a
continuous-
throughput press.
s Such a release-agent applicator is known where an applicator roller is
pressed
against a press belt where it passes over a deflecting roller to apply release
agent to the
press belt. The release agent prevents caking of the pressed material onto the
press belts
in the work area of the continuously running press. Such a continuous-
throughput press
has an upper and a lower endless belt which are each typically made of steel
and
to supported in the working region on rollers extending across heated platens
so that
pressure and heat can be transmitted through it to the material being pressed.
With the
known release-agent applicators the release agent is sprayed through a
manifold pipe
onto the applicator roller. Such spraying is a problem because on the one hand
it does
not ensure uniform application of the release agent to the press belt and on
the other
15 hand it creates a cloud of spray that is not environmentally friendly and
that normally
requires that specific protective measures be taken (EP 0,642,841).
In addition a coater device is known for coating metal belts with for example
a
plastic or lacquer layer, this coater generally comprising a doctor-blade
chamber, a
dosing roller, and an applicator roller. The doctor-blade chamber, dosing
roller, and
ao applicator roller are adjustable independently of one another (see DE 195
42 097). This
development has no bearing on the actual construction of the applicator.
Finally a device is known for applying fluent media to a web or roller by
means
of a dip or transfer roller and an applicator roller. The applicator roller is
comprised at
least partially of magnetizable material, has no axial bearing, and rolls on
the transfer
a s roller and is movable relative to the point of application (see WO
87/01308).
It is an object of the invention to provide a release-agent applicator of the
above-
described type by means of which a dosed and thoroughly uniform application of
the
release agent on the press belt is achieved, and that is environmentally
friendly and not
impractical.
3 o The invention attains this object with a release-agent applicator for a
moving
(over a deflecting drum) press belt of a continuous-throughput press, having
an
CA 02535954 2006-02-15
applicator roller pressable against the belt (adjacent the deflecting drum), a
dosing roller
pressable against the applicator roller and sitting in a release-agent bath,
actuators for
adjustably positioning the dosing roller relative to the applicator roller and
the applicator
roller relative to the belt with a pressure determined by the amount of
release agent to be
s applied to the belt, and control means for regulating the pressures
depending on the
required amount of release agent. The applicator roller transfers the release
agent to the
belt, which normally is a steel or mesh belt. The amount of transferred
release agent is
determined by the extent of surface contact between the dosing roller and
applicator
roller and between the applicator roller and the belt and thus depends from
the pressures
1 o applied so that changing the pressures applied varies the release-agent
application or the
amount transferred. Thus for example when a thin coating is needed to make
thin
pressed product, a large roller-contact area and correspondingly large
pressure is needed
while oppositely when a thick coating is needed for the production of thick
pressed
product a small roller-contact area and corresponding small pressure is
needed. In both
i5 cases it is possible to accurately dose and uniformly control the coating
of release agent.
In addition such a release-agent applicator is environmentally friendly and
eliminates
the need for special protective measures.
Further inventive features are described below. Thus the applicator roller has
a
compressible outer layer, for example is formed as an elastomer-coated roller,
in order
a o to achieve an optimal release-agent transfer. The same is true also for
the dosing roller
that can be a raster roller, for example having a structured outer surface so
as to perfectly
apply the release agent to the applicator roller. According to the surface
pattern on the
raster roller it is also possible to influence the amount of liquid pickup.
Independently it
is also possible to provide the dosing roller with a predosing doctor blade
and the
as applicator roller if necessary with a dosing doctor blade so that excess
release agent can
be scraped off. Furthermore according to the invention the pressure applied by
the
applicator roller and/or the dosing roller is monitored by pressure sensors,
pressure bolts,
pressure measurers, or pressure cans and passed as digital or analog signals
through
amplifiers to the control means. The positions of the rollers, for example the
active and
3 o inactive positions of the applicator roller and of the dosing roller, are
monitored and
reported by initiators, pressure switches, and/or end switches. Also in
accordance with
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CA 02535954 2006-02-15
the invention the applicator roller and the dosing roller are movable, e.g.
pivotal, into
their positions, e.g. pneumatic actuators as positioning apparatus by piston-
cylinder
units. Thus, for example a pressure switch can produce an output when there is
enough
pneumatic pressure available for control. The position of the dosing roller
with respect
s to the applicator roller and of the applicator roller relative to the press
belt can be
determined for example indirectly by measuring the pressures they exert. To
this end
the roller actuator can be provided with a pressure sensor. The control of the
applied
pressure is done by means of proportional valves that control the pressure of
the
pneumatic cylinders. The controller takes into account a maximum level for the
applied
i o pressures. This maximum level is then split up into right- and left-end
signals for the
applicator roller and for the dosing roller. According to the invention the
applicator
roller and the dosing roller are driven synchronously with respect to each
other and to
the belt in order to prevent premature wear and damage to the roller surfaces.
According to the invention it is possible for the applicator roller or the
working
i5 roller and the dosing roller or its support to be independently pivotal on
a frame.
According to a preferred embodiment, the applicator roller is rotatably
mounted on a
support that is pivotal on at least one frame and the dosing roller is
rotatably mounted on
at least one respective support that is pivotal on the applicator-roller
support. In this
manner the settings are interrelated in order in particular to be able to
control the roller
a o pressures reproducibly and independently of each other. It is also
possible to pivot the
two roller ends independently of each other in order to achieve fine control
of the
applied pressure over their length.
In fact a substantial feature of the invention is the independent
adjustability of
the supports at the ends of the applicator roller and if necessary at the ends
of the dosing
25 roller tin the tenth-millimeter range relative to the steel belt along its
width. In order
that the positions of the applicator roller and if necessary also of the
dosing roller does
not cause dislocation with too great a pressure/travel difference, supports at
both ends of
the applicator roller and if necessary at both ends of the dosing roller
support for the
dosing roller are interconnected by synchronizing shafts that limit the extent
of relative
3 o pivoting between the applicator-roller supports and if necessary between
the applicator-
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CA 02535954 2006-02-15
roller supports. This effect can also be achieved by synchronizing or torque
shafts,
taking into account a predetermined bearing play with spring biasing.
Finally, the invention proposes that the release-agent bath be provided in a
release-agent trough or in a doctor-blade chamber. When a doctor-blade chamber
system
is used, it is possible to mount the release-agent bath either underneath the
rollers in
horizontal orientation, or lateral of the rollers in vertical orientation.
The upper press belt as well as the lower press belt of the continuous-
throughput
press are provided with their own release-agent applicator, preferably at the
intake end.
The invention is more closely described in the following with reference to
only
i o one exemplary embodiment and with reference to a drawing. It shows
FIG. 1 a schematic side view of a continuous-throughput press with release-
agent
applicators at its intake region;
FIG. 2 a detail view of the structure of FIG. 1 in the region of the release-
agent
applicator for the upper press belt in the maintenance or waiting position of
the dosing
i5 roller and applicator roller;
FIG. 3 the structure of FIG. 1 in the active position of the dosing roller and
applicator roller;
FIG. 4 a variation on the structure of FIG. 3;
FIGS. SA, SB, and SC schematically the structure of FIG. 4 in different
a o operational positions;
FIG. 6 a top view of the applicator roller of FIG. 4; and
FIG. 7 another variant on the structure of FIG. 3.
The drawing shows a continuous-throughput press for making wood panels and
having a release-agent applicator 1 for one of two press belts 3 passing over
deflecting
2 5 drums 2. To this end FIG. 1 only shows one release-agent applicator 1 for
the upper
press belt. In addition (or alternatively) a further (unillustrated) release-
agent applicator
can be provided for the lower press belt.
The release-agent applicator 1 has an applicator roller 4 that can be set
against
the press belt 1 for example at the upstream deflecting drum 2 and a dosing
roller 6 that
3 o can be set against the applicator roller 4 and that is partially immersed
in a release-agent
bath 5. In addition, the release-agent applicator 1 has respective actuators 7
for
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CA 02535954 2006-02-15
adjustably pressing the dosing roller 6 against the applicator roller 4 and
the applicator
roller 4 against the belt 3 with a pressure determined by the amount of
release agent to
be applied to the belt. In addition there is an unillustrated controller for
regulating the
pressures in dependence on the required amount of release agent.
s The release-agent bath 5 according to FIGS. 2 and 3 sits in a release agent
trough
8. The applicator roller 4 has a compressible outer layer 9 and thus is
constructed as an
elastomer-coated roller. The dosing roller 6 is a raster roller with
structured surface. In
addition, a predosing doctor blade 10 is juxtaposed with the dosing roller 6
and a dosing
doctor blade 11 with the applicator roller 4. The contact pressures of the
applicator
io roller 4 and to the dosing roller 6 are determined in this embodiment by
pressure sensors
and transmitted via amplifiers as electrical signals to the controller. The
illustrated
roller positions, that is the active position (FIG. 3) and the maintenance
position (FIG. 2)
of the applicator roller 4 and dosing roller 6 are continuously reported and
monitored by
initiators, pressure switches and/or end switches. The maintenance position of
FIG. 2 is
i5 also a rest position for the case when the release-agent applicator is not
needed, e.g.
while production is stopped. For movement from the active to the rest position
it is
preferred to first pivot the two rollers 4 and 6 together away from the belt 3
and to then
pivot the dosing roller 6 away from the applicator roller 4.
The applicator roller 4 and the dosing roller 6 are pivoted by respective
piston-
ao cylinder units. e.g. pneumatic actuators 7 into their positions.
Servomotors drive the
applicator roller 4 and the dosing roller 6 synchronously with each other and
with the
press belt 3.
While as shown in FIGS. 2 and 3, the working roller 4 and the dosing roller 6
are
movable independently of each other via one or more supports by respective
piston-
a5 cylinder units 7, FIG. 4 shows an embodiment where the applicator roller 4
is rotatably
supported on one or more supports 12 that are pivoted on a frame 13 fixed to a
roller
support W, while the dosing roller 6 is rotatable on supports 14 that are
pivotal on the
applicator-roller supports 12. Thus the dosing roller is not completely
independently
mounted on the base, but is carried on the applicator-roller support 12. The
applicator-
3 o roller support 12 thus can be an L-shaped beam. A comparison of FIG. 4
with FIGS.
SA, SB, and SC also shows how the rollers 4 and 6 are shifted from the active
position to
CA 02535954 2006-02-15
the inactive position. To start, the first piston-cylinder unit 7a pivots the
applicator-
roller support 12 so that the applicator roller 4 and the dosing roller 6 are
jointly pivoted
back (FIG. SB). Then actuation of the second piston-cylinder unit 7b pivots
back the
dosing-roller support 14 without moving the applicator roller 4 (see FIG. SC).
s Furthermore, FIG. 6 is an embodiment where the two ends of the applicator
roller 4 are pivotal independently of each other so as to control the applied
pressure over
its length. To this end the applicator roller 4 is mounted at both ends in
pivotal bearings
15. In order to limit the extent of pivoting on the right and left sides,
there is a
synchronizing shaft 16 that prevents one of the journals 15 from swinging
completely
io out. The same or a similar device can also be provided for the dosing
roller 6.
Finally, FIG. 7 shows a variation on the invention where the release-agent
bath 5
is positioned in a doctor-blade chamber 17. The dosing roller 6 is partially
immersed in
the release agent in the chamber and the chamber is defined by two doctor
blades 18.
The use of a doctor-blade system makes it possible to vary the coating
thickness. In this
i 5 embodiment the doctor-blade unit 17 is underneath the dosing roller 6 and
thus extends
generally horizontally. In another embodiment it would be possible to arrange
the
doctor-blade unit vertically so that it is on the side of the dosing roller.
This
embodiment is not shown in the figures.
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