Note: Descriptions are shown in the official language in which they were submitted.
CA 02217801 1997-10-30
IMPROVED APPARATUS AND METHOD FOR APPLYING
A VISCOUS LIQUID TO A MATERIAL SURFACE
Backqround of the Invention
The present invention pertains to viscous
liquid applying apparatus useful in applying a wide
variety of liquid adhesives to web, sheet materials, or
other surfaces. The apparatus and related method are
particularly useful in the manufacture of corrugated
paperboard products.
10- Summary of the Invention
In accordance with the present invention, an
applicator apparatus for applying a liquid adhesive or
other viscous liquid to a moving material surface
comprises a supply of adhesive, a cylindrical applicator
roll rotatably mounted to bring an outer surface portion
into operative communication with the supply of adhesive,
a metering doctor blade positioned to engage the outer
surface of the applicator roll downstream of the adhesive
supply, the metering blade being provided with a roll-
engaging edge defined by a series of spaced notchesseparated by straight edge portions, such that the
notches form a series of spaced parallel beads of
adhesive along the roll outer surface and the edge
portions wipe the adhesive from the roll surface between
the beads, and means downstream of the metering blade for
spreading the adhesive beads laterally across the roll
surface and for moving the surface to be coated generally
tangentially along and in contact with the roll surface
in the direction of rotation to transfer the adhesive to
the surface. The metering blade is preferably mounted
with the edge oriented in the upstream direction to
provide a reverse angle of attack.
The means for spreading the adhesive beads
comprises a flexible tongue which lies on and is
resiliently biased against the surface of the roll
downstream of the doctor blade and spreads the beads into
an even and uniform film. A film control system utilizes
microprocessor control to monitor the amount of glue
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consumed, compare the amount with the known amount of
glue to be applied to the paper and the paper speed, and
controls the amount of glue supplied to the glue pan,
where a level sensor monitors the amount of glue actually
being transferred. Glue pan level data can be processed
to vary the attack angle of the doctor blade, thereby
varying the glue film thickness and thus the amount of
glue applied to the paper.
The film control system may also be utilized
10- with a chambered doctor blade or a manifold glue supply
system, using the same basic strategy and feedback
~ control.
The invention also includes an adjustable
glue layer width control which is operable to scrape glue
layers from opposite lateral edge portions of the roll
where no glue is desired, either because of changes in
web width or the width of the glue layer desired to be
applied to the web.
Brief DescriPtion of the Drawinqs
FIG. 1 is a side elevation view of an
adhesive applicator apparatus of the present invention
shown applying adhesive to a single face corrugated
paperboard web, including a schematic representation of
the glue film control system.
FIG. 2 is a side elevation of an adhesive
applicator of an alternate embodiment utilizing a
chambered doctor blade arrangement.
FIG. 3 is an enlarged side elevation of an
adjustable glue roll wiper system utilized in the FIG. 2
embodiment to adjust the width of the glue layer to
accommodate variations in web width.
FIG. 4 is a sectional detail taken on line 4-
4 of FIG. 3.
Detailed DescriPtion of the Preferred Embodiment
The adhesive applicator apparatus of Fig. 1
is shown specifically for gluing the flute tips of a
single face web 14, for example, just prior to applying
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the liner to form a double face web in a double backer.
In this embodiment, a glue roll 45 is rotatably supported
above a glue pan 46, so that the lower portion of the
roll rotates into and picks up glue from the pan. A
reverse acting doctor blade 47 of the type described in
U.S. Patent No. 5,628,868 is positioned to form glue
beads on the roll surface 50, which beads are
subsequently spread to form a continuous layer by contact
with a downstream flexible spreader tongue 51. The
single face web 14 is moved generally tangentially over
the glue roll 45 where the flute tips 17 contact and pick
up laterally extending lines of adhesive from the layer
on the roll surface 50. A backing roll 52 is preferably
positioned against the liner side 12 of the web in a
position set to accommodate the thickness of the web and
the amount of glue to be transferred from the roll to the
flute tips 17. Glue which is not transferred to the web
and remains on the roll surface 50 may be scraped
therefrom by a reverse acting scraper blade 53 so that
fresh glue is applied to the surface of the roll as it
enters the reservoir or glue pan 46. The scraper blade
53 may be submerged in the liquid glue, as shown, so the
glue is returned directly to the supply in the pan.
A spreader assembly 150 includes the spreader
tongue 151 which engages the beads of adhesive and
spreads them into a thin uniform layer. The area under
the tongue 151 is subjected to varying amounts of
downward force, depending on the thickness of the film at
a particular point, so that the equilibrium point is a
perfectly even and uniform film.
The tongue is formed of a flexible sheet
material, most preferably a plastic material having a
thickness in the range of about .005 to .120 inch (.13 to
3.05 mm). The tongue is sufficiently long so that it
wraps, via its inherent flexibility, around the roll
surface 50 for a significant distance, for example, about
12 inches or 30 cm. If a longer tongue is utilized, it
- CA 02217801 1997-10-30
is believed that no improvement in the uniformity of the
glue film results and more power is required to drive the
roll. It is also important that the downstream end of
the tongue 151 i~ formed with a sharp corner 157 to
ensure a smooth deposition of the thin film. The tongue
is supported by a rod 153 or any other suitable means.
The tongue 151 achieves uniform coating thickness because
any portion of the coating that extends above any other
portion under the tongue is immediately subject to a
downward force normal to the tongue which, in turn,
causes material to flow sideways, always toward a more
uniform surface condition.
The amount of glue transferred to the web 14
is controlled by a film control system 160, operated by a
control unit 162, which may be a portion of digital
computer or other control means 161 employed to control
the entire system. The amount of glue that should be
applied to the web 14 is a constant amount per unit of
paper contact area, and the control system utilizes that
known quantity, along with the speed of the web moving
over the roll 45 as determined by speed sensor 163 on the
backing roll 52, to calculate the amount of glue that
should be consumed per unit of time. That quantity is
then input to the control unit 162, which in turn
com~n~q a constant volume pump 164 to provide that
amount of glue to the glue pan 46 from glue reservoir
165. Control unit 162 also employs a level sensor 166 to
determine the level of glue in the glue pan 46 (which
provides an indication of whether the system is in fact
transferring the desired amount of glue to the web 14).
The control unit 162 uses the level information to vary
the angle of attack of the notched doctor blade 47, via
blade position monitor and control 168, to vary the glue
bead thickness and thus the amount of glue applied to the
web.
In the glue applicator 60 shown in FIG. 2, a
chambered doctor blade 61 is utilized. The chambered
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doctor blade includes a reverse acting notched doctor
blade 62 similar to the doctor blade 47 of the FIG. 1
embodiment. Notched doctor blade 62 is mounted at a
fixed angle and may include relatively larger holes than
blade 47 previously described. The inlet to the chamber
is closed by a forward running flexible doctor blade 63
which seals the chamber, but allows the glue remaining on
the glue roll 64 to re-enter the doctor blade chamber 65
by passing under the flexible rubber blade 63.
Fresh glue is pumped into the chamber 65 by a
variable volume pump 66 withdrawing glue from a reservoir
67. The pump is operated to supply glue to the chamber
at a rate equal to that desired in terms of a constant
amount per unit paper contact area (e.g. pounds of glue
per 1,000 square feet of paper processed) or a similarly
appropriate value. Added to the doctor blade chamber 65
is the recirculated glue passing beneath the flexible
rubber tongue 63 which is mixed with the fresh glue
supplied from the reservoir 67. Because the notched
reverse acting doctor blade 62 is mounted in a fixed
position, an increase in the level of glue in the chamber
65 will result in an increase in the pressure head
therein and, as a result, more glue will be forced past
the notches in the doctor blade 62. Downstream of the
chamber doctor blade, the glue beads are spread with the
use of a flexible tongue 151 which may be identical to
that described with respect to the FIG. 1 embodiment.
Utilizing a feedback film control system
similar to system 160 described with respect to FIG. 1,
the glue level in the chamber 65 is monitored to provide
the appropriate control signals to operate the metering
pump 66 to maintain the flow through the notched doctor
blade 62 to maintain the desired film to be applied to
the single face web 68 or other web being coated.
Referring to FIGS. 3 and 4, one of the
problems with metering-type glue rolls 64 of the type
described above is that it is difficult, cumbersome or
CA 02217801 1997-10-30
messy to control the width in the cross machine direction
of the glue layer to be applied, either because less than
the full width of the web 68 is desired to be coated or
because a narrower web is being run. In either event,
the glue layer outside the width desired to be applied is
typically removed by the use of glue dams. In accordance
with this invention, the glue layer is applied to the
full width of the roll 64 and an adjustable reverse
operating doctor blade 70, positioned just upstream of
the application point to the web 68, is utilized to
scrape the glue layer from the portion of the roll 64
where no glue is desired and to return the glue to the
system for reuse. The flexible wiper blade 70 is
utilized with an identical blade mounted at the opposite
axial end of the glue roll 64, both of which operate
identically. The wiper blade 70 is fed laterally across
the roll surface from a blade source 71 to contact the
portion of the roll surface where it is desired to wipe
the roll clean and remove all the glue. The blade 70
runs in a track 72 in a glue collection trough 73 and is
biased into contact with the surface of the roll with an
appropriate biasing leaf spring 74 or the like.
The film control system 160 described
hereinabove utilizes strategy which may be applied to
control the film thickness in a manifold-type glue supply
system as well. In such a system, the metering supply
pump would be operated, as previously described, to
deliver glue at the desired output rate to a delivery
manifold located adjacent the rotating glue roll from the
surface of which all glue had previously been removed.
The metered volume of glue is delivered to the roll
surface directly upstream of the flexible rubber
smoothing blade or tongue where it is smoothed into a
uniform layer and delivered for direct application to the-
web. Any glue that is not used, either because it wasnot picked up by the web or because it was removed by the
width control system (FIGS. 3 and 4), would be returned
CA 02217801 1997-10-30
to a reservoir which also contains the new feed stock
glue. By monitoring the level of the glue in the
reservoir, the comparison may be made between the
calculated amount being pumped to the manifold and the
amount actually being utilized. The appropriate feedback
control signal may then be utilized to vary the pump
speed to adjust the amount fed into the manifold. In the
case of applying glue to the flute tips of a single face
corrugated web 68, as shown in FIG. 2, as an example, an
increase in the amount of glue supplied to the manifold
will result in an increase in the thickness of the glue
layer applied to the roll 64. This in turn would
increase the pickup rate by the flute tips of the
corrugated single face web traveling over the surface of
the glue roll 64.
