Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the processing of semi-
pourable fibrous elements such as or having dimensions
similar to woodenwafers, flakes or shavings in order to form
a continuous uniform stream of separated wooden elements
or particles available for uniform distribution in forming a
mat.
In the operation of layin~ down a uniform mat of semi-
pourable fibrous materials, such as short lengths of wooden
strands, or wooden wafers such as described in V.S. Patent
No. 2,776,687, generally satisfactory separation for doing
so is described in U.S. Patent No. 3,881,225. As described
in the aforementioned patent, a constant stream of particles
is carried by a conveyor to the apparatus and removed from the
end of the conveyor by a rapidly moving spike roll which claws
off particles from the end of the oncoming stream, which
particl~s are then fed into the depositing apparatus.
The spike roll is necessary because, if it is not
used for semi-pourable particles, especially if they are
rough and hairy or damp, the particles will break off from
the conveyed stream as they are being discharged to form
large clumps or clusters. The spiked roll serves markedly to
reduce the size of these clumps, but if the particles are
long, and especially if their surfaces are not smooth, when
they are clawed off, each particle almost invariably brings
adjacent particles with it, thus forming an ununiform stream
of small clumps. In fact, if the stream is not large, it
may even become disconnected whereby it becomes difficult
if not impossible by known means to spread and ~istribute
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such streams of particles into a uniform, smooth mat.
It is an object of this invention to provide a method
and means or breaking up such clumps or clusters of fibrous
particles whereby the latter issue smoothly as a uni~orm stream
of separated particles capable of being spread onto a continuously
moving surface to form a smooth and uniform mat thereon.
In accordance with the invention in one aspect there is
provided a method of feeding semi-pourable fibrous particles which
tend to cling together as clumps or clusters to appar~tus that
serves to orm the particles into a structure; the me-thod comprising
the steps of first feeding the particles in-to the upper portion of
a downwardly inclined conveyor and, under the influence of
gravitational force and the motion of the conveyor, agitating the
particles during their downward movement throu~h the conveyor to
cause clusters of particles to be broken up and spaced longitudinally
thus causing the particles to issue from a lower portion of the
conveyor as a smooth, continuous uniform stream which is then fed
directly to said apparatus.
The invention in a further aspect provides in the
2~ manufacture of an air-laid structure consisting mainly of semi
pourable particles, involving the txansformation of a metered
stream of said-particles into a stream of continuously uniform
cross-section, the step of feeding said stream into the upper open
end of a downwardly slanting rotating tube having a cross-section
many times the area of said stream whereby lumps in the feed stream
are dispersed and smoothed and feeding the resulting uniform stream
issuing from the lower end of said tube to a distributing means to
form said structure.
These and other objects and advantages of this invention
will hereinafter appear and for purposes of illustration,but not of
limitation, embodiments of the invention are shown in the
accompanying drawing in which:
Figure 1 is a plan view in side elevation of an
apparatus embodying the features of this invention,
Fi~ure 2 is an end view of the apparatus shown in
Figure 1, and
Figure 3 is an end view of a modification of the
apparatus of this invention.
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It has been found that if such a stream containing small
clumps of wooden wafers or other .~ibrous elements that are incapable
of matting or clinginy together is fed into an inclined, open
ended, revolving tubular member having a rough internal surface which
serves bo lift the particles and allows them to fall back down during
rotational movement, the clumps will be dispersed as the particles
progress down the inclined tubular member so that they will be
discharged from the exit end of the tubular member as a smooth and
steady stream substantially ~ree of clusters. If the particles are
slender, as compared to their length, especially if they also have
rough surfaces or are curled, they are relatively nonpourable,
except in the form of large clus-ters. However, by passing down a
rotating, inclined tubular member of adequate length and diameter,
they will issue in a stream as smooth and steady as if they were .
completely pourable. This assumes that the particles are not so
long and so fine that they will cling firmly together and the
action provided cannot separate one from anotherO
Referring now to the drawings, a metered stream
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of semi-pourable fibrous particles 10 is shown as being
transported on the upper run of an endless belt 11 opening
in a trough 12, at the end of which there is pro~ided a
rapidly revolving spiked roll 13. The spiked roll claws
particles and clumps of particles off the conveyor onto a
downwardly inclined chute 14 and into the upper open end
of an inclined tubular member 15 mounted for rotational
movement. The inner surface of the tubular member 15 is
roughened, such for example as by a number of longitudinally
extending corrugations 16 or projections. If there is not
suf~icient room availahle for a long tubular member, under
some condi-tions or restrictions, a collar 17 may be provided
as a dam at the exit end of the tubular member whereby the
number of particles retained in the t~bular member is markedly
increased before overflow. The disintegxation of clumps or
clusters for separation is enhanced by reason of the additional
work performed during the tumbling action of such higher
concentration of fibrous particles.
The stream 19 issuing from the end of the tubular member
is particularly well adapted for feeding directly into some
form of particle distributing apparatus, suc~ as the felter
described in U.S. Patent No. 3,881,225 to form a smooth,
clump-free mat on a continuously moving collecting surface.
Experiments were conducted with a tubular member having
a length of 2 meters and an internal diameter of 45 cm. A
thin metal sheet was fixed as a lining on the inner surface
with circumferentially spaced apart corrugations extending
lengthwise along the axis of the tubular members. One hundred
30 grams of wooden wafers each having a dimension of about -~
65 x 25 x 0.8 mm. were packed together in a round heap at
the upper inlet end of the tubular member. The tubular member
was rotated at various speeds within the range of 25 to 60
rpm and with the tubular member inclined at various angles
within the range of 5 to 12 with the horizontal. The most
most favorable conditions with the described apparatus was --
a speed of about 40 rpm at an angle of 8. Under these
conditions, the particles began to issue as a smooth stream
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from the exit end beginning at 7 seconds and terminatingat about 13 seconds. The wafers issued at a uniform rate
after a steady state was reached through the period of 7 to
13 seconds. At an angle of 12, the resident time within
the tubular member was from 5 to 9 seconds, depending on
the speed of rotation.
It will be obvious that the continual addition of
clusters of wafers to the upper feed end of the rotating
tubular member will enable it to deliver an unexpectedly
uniform and continuous smooth flow of particles from the
lower exit end.
Because of the difficulty of feeding a uniorm
s~ream of fibrous materials into a felter of the type
described in U.S. Patent No. 2,770,844 despite its other-
wise obvious advantages, it has not been widely used. The
method of this invention provides, for the first time,
means for converting a stream of resinous coated elongate
fibrous particles for feeding a device o~ the type described
in the aforementioned patents whereby a uniform mat can be
obtained on a movin~ collecting surface and a board can
be obtained by compression at elevated temperature having a
hitherto unobtainable uniform density throughout the cross
section. The latter is very important since, if the body
of the board is formed containing aggregates of fibrous
particles, the smooth flat surface imparted by the press will
subsequently become uneven when the board is exposed to
moisture or high humidity or, if such a board is veneered,
the denser aggregates and the areas of lesser density will
be "telegraphed" to the outer surface of the veneer and ruin
its appearance.
The extent to which the bundles or semi-pourable
wooden or fibrous particles or wafers are subjectea to the
tumblingaction for separation will depend somewhat on the
angle of inclination of the tubular member, its diameter,
length, and rate of rotation. The rate of rotation of the
tubular member should be less than that at which the
particles will be held at centrifugal force to the walls
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of the tubular member unless the modified apparatus shown
in Fig. 3 is employed. With a diameter of about 30-60 cm
the desired results can be achieved with a rate of rotation
within the range of 10 to 75 rpm and preferably about 30
to 50 rpm.
The angle of inclination can be varied through a wide
ran~e depending on the dimensions oE the apparatus, but it
is preferred to dispose the tubular member having approximately
the dimensions and conditions previously discussed for
rotation about an axis inclined at an angle within the range
of 5-15 and preferably 6-10 with the horizo~tal. The length
of the tubular member will depend somewhat upon the angle of
inclinatlon, as indicated in the preceding example. Under
the conditions described wherein the tubular member is dis-
posed at a slope of 5-15, revolves at a rate of 15-75
rpm and has an internal diameter within the range of 30-60
cm, the desired results can be achieved with a tubular member
having a length of from 1 to 5 m. It is desirable to make
use of a length whereby the resident time of the particles
for tumbling action within the tubular member will be at
least 5 seconds and more if the particles are not easily
separated. While the resident time can exceed one minute,
little if any additional benefit is achleved.
The desired configuration or surface roughness on
the inner wall of the tubular member or trough can be achieved
by the use of spaced longitudinal narrow strips of metal~
Alternatively, the surface configuration can be in the form
of corrugations, dimples, cross hatching or in the form of
an abraded surface to which the particles will tend to cling.
As indicated in Fig. 3, it is possible to achieve the
objectives by speeding up the tubular member sufficiently
to cause the particles to cling to the surface by centrifugal
force, then use a long scraper fixed along the top of the
member to remove and agitate them so they fall and progress
down the tube. The angle of inclination of the member may
then be increased beyond 15 if desired.
It will be understood that changes may be made in
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the details of construction, arrangement ~nd operation with-
out departing from the spirit of the invention, especially
as defined in the following claims.
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