U.S. patent number 3,916,825 [Application Number 05/425,135] was granted by the patent office on 1975-11-04 for apparatus for coating fibers with binder to produce fiberboard.
This patent grant is currently assigned to E. Schnitzler GmbH & Co.. Invention is credited to Erwin Schnitzler, Ulrich Schnitzler.
United States Patent |
3,916,825 |
Schnitzler , et al. |
November 4, 1975 |
Apparatus for coating fibers with binder to produce fiberboard
Abstract
An arbor having arms is rotated in a drum such that the ends of
the arms sweep the inner wall of the drum and advance a mass of
fibers or chips as a flowable fleece along the drum from an inlet
to an outlet thereon. The inside wall of the drum is provided with
at least one V-shaped baffle extending radially in from this wall
and directed in the direction of displacement of the fleece so that
it forms a dead-fluid region and a vortex street in the fleece. The
binder is injected into the fleece at the dead-fluid region and
mixes with the fibers in the vortex street. The baffle has relative
to the arbor rotation axis a tangential length and a radial height
both many times greater than the average fiber length.
Inventors: |
Schnitzler; Erwin (Karlsruhe,
DT), Schnitzler; Ulrich (Reichenbach, DT) |
Assignee: |
E. Schnitzler GmbH & Co.
(Karlsruhe, DT)
|
Family
ID: |
5864562 |
Appl.
No.: |
05/425,135 |
Filed: |
December 17, 1973 |
Foreign Application Priority Data
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Dec 15, 1972 [DT] |
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2261598 |
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Current U.S.
Class: |
118/303;
366/172.1 |
Current CPC
Class: |
B27N
1/0245 (20130101) |
Current International
Class: |
B27N
1/00 (20060101); B27N 1/02 (20060101); B05C
005/00 () |
Field of
Search: |
;118/303,19,418
;259/26,25,9 ;117/109,1A |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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149820 |
April 1874 |
Wilkie |
254371 |
February 1882 |
Puffer et al. |
3130070 |
April 1964 |
Potters et al. |
3346240 |
October 1967 |
Lavelle et al. |
3841262 |
October 1974 |
Groppenbacher et al. |
|
Primary Examiner: McIntosh; John P.
Attorney, Agent or Firm: Ross; Karl F. Dubno; Herbert
Claims
We claim:
1. An apparatus for coating fibers with a binder, said apparatus
comprising:
a drum having an axis and an axially spaced inlet and outlet;
an arbor extending axially in said drum and having axially spaced
radially extending arms with ends adjacent the inner wall of said
drum;
at least one baffle on said inner wall between axially spaced arms
having a height in a radial direction and a length in a tangential
direction, each many times greater than the average length of said
fibers, said baffle having a pair of sides inclined to the
direction of displacement of said fleece thereby and terminating in
a common apex pointing opposite this displacement direction;
means for relatively rotating said arbor and said drum with said
ends of said arms sweeping said inner wall for displacing said
fibers from said inlet to said outlet as a fluid fleece lying in a
layer of limited thickness along said wall and forming a dead-fluid
region in back of said baffle;
at least one nozzle on said inner wall of said drum in said dead
fluid region directly in back of said baffle and between said
sides; and
means for introducing binder into said drum through said nozzle,
said fleece being advanced at a rate to form a vortex street in
back of said dead-fluid region, said binder being injected at a
volume rate per unit time equal to generally half the rate
sufficient to eliminate said vortex street.
2. The apparatus defined in claim 1 wherein the radial height
divided by the fiber length is greater than three and less than
seven.
3. The apparatus defined in claim 1 wherein the tangential length
of said baffle divided by the fiber length is greater than three
and less than seven.
4. The apparatus defined in claim 1 wherein said drum is
non-rotatable and said arbor and arms are rotatable about said
axis.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus for coating fibers or
chips. More particularly this invention concerns a system for
producing a mass of binder-coated fibers or chips for the
production of fiberboard.
BACKGROUND OF THE INVENTION
The fibers, here including chips or other elongated pieces of
material used in the production of construction chipboard or
fiberboard (pressed board), are usually fed into a horizontal
cylindrical drum at one end. This drum is rotated or an axially
extending arbor in the center of the drum is rotated so that arms
on this shaft displace the fibers axially toward an outlet. Binder
in liquid form is injected into the drum usually through nozzles
which open either radially or tangentially relative to the inner
surface of the drum.
In order to prevent the fibers from being damaged, the rotation
speed is generally maintained high enough so that the mass of
fibers forms a cylindrically hollow body or fleece lying against
the inside of the drum, with the ends of the advancing or mixing
arms serving to mix the binder with the fibers. Too slow a rotation
speed causes the fibers to tumble and break. The so coated fibers
are then formed into mats as discussed in the commonly assigned
U.S. Pat. No. 3,655,098 of Ulrich Schnitzler. The mats are then
pressed into rigid boards.
As a rule it is almost impossible to achieve a uniform binder
coating over each fiber. Even though it is possible in such devices
to mix the binder well with the fibers, many fibers are frequently
left wholly or partially uncoated, which causes weaknesses in the
finished board. Excessive mixing does little to remedy this
situation, and often destroys the fibers.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an
improved apparatus for the coating of fibers.
Another object is the provision of an improved system which
uniformly coats fibers for the production of fiberboard.
A further object is to provide a coating system which overcomes the
above-given disadvantages.
SUMMARY OF THE INVENTION
These objects are attained according to the present invention in a
system wherein the interior of the coating drum is provided with at
least one baffle which forms in the flowable fleece in the drum a
dead-fluid region. A nozzle in this dead-fluid region injects
binder into the flowable fleece being displaced from the inlet to
the outlet of the drum by the arms of an arbor which sweep the
inner wall of the drum. In this manner a vortex street is formed in
back of the baffle, which according to this invention has a
tangential length and a radial height which are both substantially
greater than the average fiber length.
In accordance with further features of this invention the binder is
injected at a rate (volume/unit time) which is between 45 and 55
percent the rate necessary to eliminate separation in back of the
baffle. This principle is discussed at pages 9-28 and 9-29 of the
Handbook of Fluid Dynamics edited by V. Streeter (McGraw Hill:
1961). In this manner a vortex street is maintained downstream in
back of the baffle for best mixing of the binder and the
fibers.
DESCRIPTION OF THE DRAWING
The above and other objects, features, and advantages of the
invention will become more readily apparent from the following
description, reference being made to the accompanying drawing in
which:
FIG. 1 is a longitudinal section partially in diagrammatic form
through the apparatus according to this invention;
FIG. 2 is a cross section taken along line II--II of FIG. 1;
FIG. 3 is a view of the detail indicated by arrow III of FIG.
2;
FIG. 4 is a view in the direction of arrow IV of FIG. 3;
FIG. 5 is a sectional view similar to FIG. 4 indicating another
form of this invention; and
FIG. 6 is a perspective view illustrating the functioning of the
present invention.
SPECIFIC DESCRIPTION
As shown in FIGS. 1 and 2 the apparatus comprises basically a
cylindrical treatment drum 1 formed with an inlet 2 in which fiber
from a hopper 21 is fed and formed with an outlet 3 whence the
coated fiber leaves. An arbor 4 extending along the axis A of the
drum 1 has a plurality of axially staggered and diametrically
opposed arms 5 whose ends sweep the interior of the drum as the
arbor 4 is rotated about the axis A by a drive 6. This relative
rotation, which could also be effected by rotating the drum
concurrently with or instead of the arbor 4, forms all of the
individual fibers F (FIG. 3) into a flowable fleece 9 lining the
inside of the drum 1. Two injectors 7 axially between the arms 5 at
the upstream end of the drum 1 are connected through a pipe 18 and
a pump 19 to a source 20 of fluid binder.
FIGS. 3 and 4 show how each injector 7 is formed of a generally
V-shaped baffle 10 having an apex directed against the direction D
of displacement of the arms t and of the fleece 9 and having front
surfaces 10a extending radially to the axis A. Located between the
flanks of this baffle 10 is a pair of nozzles 8 directed back in
the direction D. The baffle has a length T measured tangentially to
the drum 1 and a height R measured radially which are both
multiples of the average length L of the fibers F. The relationship
##EQU1## is maintained. Here R .apprxeq. 6L, and T .apprxeq.
5L.
FIG. 6 shows the fleece 9 as if it were planar. Here it can be seen
that a dead-fluid region 11 is formed in back of the baffle 10. A
pair of vortices 16 are formed from the normally laminar flow 15
and are shed periodically to form a Karman vortex street 17 as
discussed on page 9-6 of the above-cited Handbook of Fluid
Dynamics.
An injector 13 as shown in FIG. 5 can be used in place of the
injector 7 of FIG. 4. This arrangement is a single piece of metal
of triangular section having a pair of sides 10' constituting the
baffle and a bore 12 terminating in a pair of nozzle orifices 8'
opening in a back face 14 of the injector 13 in flow direction D.
The sides 10' have like but opposite inclinations, here 25.degree.,
to the direction D.
EXAMPLE
Fibers having a length between 1 mm and 5 mm, a width between 0.5
mm and 2 mm, and a thickness between 0.1 mm and 0.3 mm are used in
fine fiberboard, the average length (L) being 3 mm. In coarser
fiberboard the chips have a length between 3 mm and 15 mm, a width
between 2 mm and 8 mm, and a thickness between 0.4 mm and 0.5 mm,
the average length being 10 mm. Thus the dimensions T and R of the
baffle 10 and 13 lie between 30 mm and 35 mm. The flow speed in
direction D is between 20 m/sec and 35 m/sec.
* * * * *