Note: Descriptions are shown in the official language in which they were submitted.
~ 155628
SPECIFICATION
This invention relates to methods and apparatus for
uniform handling of particulate matter in the manufacture Df
composition board.
In one of its spesific aspects, the invention is con-
cerned with uniform distribution and delivery of lightweight,
comminuted fibrous material for continuous-line formation of
, fiberboard having directional properties. Examples of a light-
weight furnish handled by the present invention are the fibrous
materials produced from wood pieces by disk refining in an
attrition mill in the presence of steam at atmospheric or higher
pressure. The resultant lightweight comminuted fibrous furnish
exhibits a bulk density of about one to approximately four
pounds per cubic foot. The fibers are fine in texture, elongated,
and tend to cluster. Also, the fibers, especially wood fibers
refined with s~eam above atmospheric pressure, can exhibit
aerodynamic properties tending to diminish free-fall velocities.
It was previously considered necessary to use
pneumatic impulsion handling methods for such lightweight
fibrous furnish. However, in addition to fiber clustering
difficulties, orientation control utilizing an electric field
can be rendered ineffective because of air turbulence when
using pneumatic impulsion and obtaining the desired uniformity
of deposition becomes impracticable.
The present invention contributes controlled handling
and metering to provide continuous movement of the furnish at
a substantially constant weight-per-unit-time through the
processing line.
:
~ 1S562~
In accordance with one aspect of the present invention
. there is provided, in continuous-line manufacture of particleboard,
a method providing for uninterrupted movement of particulate
furnish through a forming line and uniformly distributing such
S furnish for delivery over a preselected area to continuously
form a mat of such furnish, comprising
providing a particulate furnish,
providing a forming line including means for feeding
furnish into the forming line located in vertically spaced
relationship from a conveyor means for deposition of furnish to
- form a mat, with the forward directi:on of movement for furnish
in the forming line being from the means for feeding furnish
into the forming line toward the conveyor means,
such conveyor means presenting a mat support web,
controllably moving such web to present a surface of
- preselected area for deposition of furnish, such web movement
establishing a forming direction for the mat being formed by
deposition of furnish,
such preselected area of deposition establishing a
dimension in the forming direction and a dimension perpendi-
cularly transverse to the forming direction,
continuously feeding furnish into the forming line,
moving the furnish fed into the forming line trans-
versely to the forward direction of movement for furnish to
: 25 distribute furnish substantially uniformly over one dimension
of the preselected area of deposition while delivering furnish
in the forward direction,
passing furnish distributed over such one dimension
of the selected area of deposition through a flow-through
header chamber while confining such furnish to a fractional
:
1 1S5~28
; portion of the remaining dimension of the preselected area of
deposition,
controllably metering removal of furnish from such
header chamber in the forward direction by continuously
removing furnish from such header chamber,
uniformly distributing such furnish over the
remaining dimension of the preselected area of deposition,
and
delivering furnish uniformly distributed over
substantially the full selected area of deposition toward the
support web along a flow path having a direction which is
substantially normal to the surface of deposition.
There is also provided in accordance with the present
invention, in the manufacture of fiberboard, a forming line
providing for uninterrupted movement of lightweight fibrous
furnish for delivery to and distribution over a preselected area
to continuously form a mat of such furnish for compaction and
curing into fiberboard, such furnish being moved continuously
through the forming line without relying on pneumatic impulsion
with movement of furnish in approaching and during orientation
for deposition being in a direction which is substantially
normal to the area of deposition and substantially free of air
turbulence comprising
means for continuously feeding lightweight fibrous
furnish into a forming line,
conveyor means located downstream from and in vertic-
: ally spaced relation to such furnish feeding means,
the conveyor means presenting an elongated support
web and including means for controllably moving the elongated
support web to present a surface of preselected area for
deposition of furnish,
-2a-
1 155628
such controlled movement of the elongated support web
establishing a forming direction for the mat being formed,
such preselected area of deposition establishing a
dimension in the forming direction and a dimension perpendicularly
transverse to the forming direction for such surface of
deposition of furnish,
means for moving furnish continuously fed into the
forming line transversely to the direction of movement of furnish
toward the support web and for continuously discharging furnish
in the direction of the support web distributed over one dimension
of the preselected area of deposition,
a flow-through header chamber for receiving furnish
distributed over such one dimension of the selected area of
deposition and confining such furnish to a fractional portion of
the remaining dimenion of the preselected area of deposition,
metering means for continuously removing furnish from
such header chamber in the direction of the support web,
means mechanically contacting such metered furnish to
accelerate movement of such furnish in the direction of the
support web,
means for uniformly distributing such furnish over the
remaining dimension of the preselected area of deposition while
maintaining such initial distribution of furnish in such one
dir.lension,
such means for distributing furnish over the remaining
dimension providing mechanical contact with such furnish and
imparting a component of movement to the furnish transverse to
its direction of movement toward the support web along the
remaining dimension of distribution to continuously deliver
-2b-
-?
.~
1 1 5562~
furnish uniformly distributed over substantially the full selected
area of deposition, and
means for directing such furnish distributed over the full
area of deposition toward means for orientation and deposition of such
furnish on the continuously MOVing support web.
Utilizing the teachings of the invention, a lightweight disk
refined fibrous furnish can be handled without relying on pneumatic
impulsion for movement of such furnish to achieve commercially acceptable
flow rates. Air turbulence effects are substantially eliminated while
providing for uniform distribution and deposition of the lightweight
furnish. Commercially economic production rates of fiberboard are made
practicable while enabling desired orientation of fibers by means of
an electric field.
The significance of these contributions and other advantages
are considered in a more detailed description of the invention which
includes reference to the accompanying drawings. In these drawings:
FIGURE 1 is a schematic view in elevation, with portions
cut away, of apparatus embodying the invention;
FIGURE 2 is a schematic cross-sectional view in elevation
of the apparatus of FIGURE 1 embodying the invention;
FIGURE 3 is an enlarged view of a portion of the apparatus
of FIGURE 2;
FIGURE 4 is a view of flow-splitter apparatus taken along
the line 4-4 of FIGURE 3;
FIGURE 5 is a view of damper-venting apparatus taken along
the line 5-5 of FIGURE 3;
FIGURE 6 is a view of shroud control apparatus taken along
the line 6-6 of FIGURE 3;
FIGURE 7 is a view taken along the line 7-7 of FIGURE 6, and
FIGURE 8 is a view taken along the line 8-8 of FIGURE 7.
~t
_
1~55628
A significant cDntribution of the inventi~n involves
continuous over-feed of furnish into the processing line to
eliminate possible problems associated with interrupted or
cyclic movement of particulate material, bulk density changes
in the material, or surges related to pneumatic transport of
furnish to inlet means for the forming line.
In a specific embodiment of the invention for
handling lightweight fibrous furnish, cyclone 10 of FIGURES
1 and 2 is provided to separate air when pneumatic flow is
used for transporting fibrous material from blended fiber bin
12 (FIGURE 1) to such cyclone hopper means. The furnish is fed
continuously from cyclone 10 into the distribution and
deposition equipment. The furnish is first distributed over
one dimension of the mat being formed; as shown, in the cross
direction i.e. perpendicular to the mat forming direction for
the line.
The furnish from cyclone 10 is fed at a rate in
excess of the mat deposition rate. Bidirectional feed screw
14 moves the furnish across the lateral dimension which is
correlated with, and preferably approximately equal to, the
lateral dimension of the mat being formed.
Discharge of furnish in the forward direction, i.e.
toward the mat being formed, from bidirectional screw 14 is
uniform across the selected dimension. Flop gates 16 and 18
at the discharge opening of cyclone 10 are adjusted so that the
quantity of furnish overflowing from the ends of bidirectional
screw is equal. Excess furnish is returned from ends of the
bidirectional feed screw 14 through vacuum return conduits 20
and 22.
115562~
The laterally distributed furnish moves in the f~rward
direction into a flow-through chamber 24 (shown partially cut
away, with a viewing glass 25, in FIGURE 1) which functions
as a metering bin fvr the furnish. Lateral distribution is
maintained in the flow-thr~ugh chamber 24 by providing a
lateral dimension which is correlated with, and preferably
substantially equal to, the lateral dimension of the mat being
formed.
The furnish is accumulated to a uniform height across
the lateral dimension of flow-through chamber 24. The continuous
flow feature made available at this stage by continuously feeding
furnish in excess of that to be distributed while returning
excess enables a constant head of furnish to be maintained in
chamber 24 without "on-off" controls. This provides more
accurate metering while maintaining the continuous fl~w taught
for avoiding the handling problems previously encountered with
lightweight furnish.
Flow-through chamber 24 includes a profiling chamber
26 at its discharge end which establishes a configuration for
the furnish which facilitates metering. Profiling chamber 26
presents a discharge opening having a lateral dimension substan-
tially equal to that of the laterally distributed furnish. One
purpose of the profiling chamber 26 is to control and maintain
uniform fiber weight over the distributed dimension. In the
illustrated embodiment the initial distribution is in the
cross-machine direction; theref~re, the profile of the furnish
in the machine-forming direction is confined to a fractional
portion of the machine-forming dimension established for mat
1 15562~
forming deposition of furnish. Compression of the furnish in
the machine-forming direction is cDntrolled, e.g. by
adjustable baffle structure 28, 30 (FIGURES 2 and 3) located
along each extended length sidewall internally of the profiling
chamber. A plurality of individually adjus~able baffles, such
as 32 (FIGURE 1) are aligned to adjust the profile. Baffle
adjusters, such as 34, 36 are connected to each such baffle.
Baffles 38 and 40 at the ends of profiling chamber 26, which
are adjustable by means of lateral adjusters 42, 44, maintain
the lateral distribution dimension for proper feeding into the
next element in the line.
Profiling chamber 26 leads into metering chamber 48
(FIGURES 2 and 3). Metering rolls 50, 52 (FIGURE 3) are
disposed in chamber 48 with their longitudinal axes of rotation
extending along the dimension of distributed furnish. Contact
surfaces of the metering rolls 50, 52 establish a cross-
sectional periphery which extends to boundaries of the discharge
opening established within the profiling chamber 26. Such
contact surfaces positively grip the furnish, compressing the
furnish in a preselected manner which facilitates metering
while moving the furnish in the forward direction. Metering
nip 54 is defined by the metering rolls 50, 52 to have
a preselected cross-sectional area. Rotation of metering rolls
50, 52 is continuous with RPM controlled to move furnish in the
forward direction at a uniform controlled rate without relying
on pneumatic impulsion.
Scalping roll 56 is positioned below the metering
nip 54. The weight of the furnish column extending upwardly
--5--
~ 15~62~
through the metering nip 54 and into chamber 24 is partially
supported by positioning of the scalping roll 56 in the flow
path from the metering rolls, generally slightly off center of
such flow path. A slot 58 for adjustable positioning of
scalping roll 56 is shown by dotted line. Such furnish
column support provides better metering control by enabling
the furnish to remain under the control of the metering rolls
50, 52 in the metering nip 54. Also, haphazard break-up of the
controlled-configuration furnish after exit from the metering
nip 54 is avoided. The furnish is delivered in a controlled
manner avoiding irregular falling or avalanching of furnish
into the next downstream element.
The RPM of scalping roll 56 is controlled to provide
a high surface velocity. Impingement on scalping roll 56 not
only provides for uniform forward movement of the furnish but
also provides forward momentum of lightweight furnish for main-
taining desired production flow rate through the processing
line during subsequent distribution over the full area of
deposition. The high surface velocity of scalping roll 56 is
impa~ted to the controllably metered furnish. Thus, accurate
metering control of a relatively slow moving compressed furnish
column is obtained at rolls 50, 52 while enabling acceleration
after metering.
It has been found that the high velocity imparted
to the furnish by the scalping roll 56 after the relative low
velocity movement through the metering rolls 50, 52 can create
a need for replacement air as the furnish is suddenly acceler-
ated. In order to avoid air flowing countercurrent to the
1 ~S562~
fDrward direction of movement of the Eurnish, air hatches are
provided to allow outside air to enter the former shell and
interior sub-structure. Such entry oE air is at a location
removed from the mat being formed so as to avoid any air
turbulence effect on the mat or any orientation function.
Entry of air into outer shell 59 of the former is
through air hatches 60, 62 (FIGURES 2 and 3). Air access
into the scalper roll area is controlled by damper means 64
(FIGURE 3) which includes a plurality of individual air
dampers, such as 66, 68 (FIGURE 5) distributed along the
lateral dimension. Damper adjustment means 70 (FIGURE 3)
provide for damper adjustment from externally of the forming
line shell, each damper, such as 66, 68, can include such an
adjustment means for uniform air admission across the distributed
dimension.
The furnish as delivered from the scalping roll 56
is moving in the forward direction at a velocity substantially
equal to the surface velocity of the scalping roll. A chute
structure is formed within the former shell to properly direct
furnish for distribution over the remaining dimension of
deposition. This chute structure can include a cleaning plate
associated with each feeder roll. As shown in FIGURE 3, clean-
ing plate 72 for metering roll 50 and cleaning plate 74 for
metering roll 52 are adjustably mounted to control contact with
each metering roll. This cleaning action preserves the gripping
strength of the metering rolls by eliminating fiber build-up.
The chute structure includes sidewalls 76, 78 (FIGURE
3) leading to the inlet side of means for distributing furnish
--7--
~ 115562~
over the remaining dimension of mat deposition. A furnish flow
splitter structure 80 (FIGURE 3) is located in the chute
downstream of the metering rolls in the direction of further
distribution means.
The high-velocity, longitudinally-confined furnish
is directed to distribution means which spread the confined
furnish over the full area of deposition. This distribution
means controllably reduces forward velocity of the furnish
while maintaining the desired constant weight per unit time
movement of furnish.
The initial distribution of the furnish which is
maintained in the flow-through chamber 24 and during metering,
is also maintained during distribution of the furnish in the
machine-forming direction, i.e. over the longitudinal dimension
of the mat being formed. Contact of the furnish with the
scalping roll 56 initiates the uniform break-~p of the metering
configuration and imparts desired forward movement to the
furnish without relying on pneumatic pressure.
After contact with scalping roll 56, the furnish is
directed toward longitudinal distribution means 82. A plurality
of distribution rolls 83 through 88 are arranged in banks to
impart a horizo~tal component of movement and to move the
furnish between and about the distribution brush rolls. Uniform
longitudinal distribution is provided along with controlled
movement of furnish in the forward direction over substantially
the full preselected area of deposition for forming a mat.
In the embodiment shown, the banks of distribution
brush rolls are arranged, when viewed axially, to form sides
1 ~5562~
of a triangular configuration having an apex portion pointed
in the direction of the scalping roll 56. A remaining side of
the triangle, opposite to such apex portion, extends over sub-
stantially the full longitudinal dimension of the area of
deposition and is disposed in the direction of the mat to be
formed.
This arrangement provides for uniform longitudinal
distribution. Also movement in the forward direction can be
carried out substantially free of pneumatically imparted velocity
so as to provide for fiber orientation by means of an electrical
field. The high forward velocity imparted by the scalping roll
56 is controlled by the longitudinal distribution brush rolls
83 through 88. ~ longitudinal movement, transverse to the
forward direction, is imparted so that discharge from the brush
rolls in the forward direction is controlled. Also, the inter-
action of the longitudinal distribution brush rolls helps to
break up large clumps of furnish which might exist.
For uniformity of distribution purposes, it is pre-
ferred to have substantially equal portions of the furnish be
handled by each half of the distribution means 82. Splitter
80 is adjustably mounted to provide the desired diversion of
furnish. As can be visualized from the detailed view of
splitter 80 in FIGURE 4, baffle structures such as 90, 91
direct a portion of the furnish toward distribution roll 83
and the open portions such as 92, 93 direct the remaining portion
of the furnish toward distribution roll 84. The distribution
brush rolls 83, 84 can be adjustably positioned by means of the
slots 100, 101 shown in dotted lines in FIGURE 3. Shroud
1 155~2~
structure 102, 104 partially surrounds distribution rolls
83, 84, respectively. Each shroud structure includes a
plurality of vanes and adjustment means. The vane structure
can be moved toward and away from the axis of the distribution
brush rolls 83 and 84 by slotted adjustment arms 110 and 112.
The vanes help guide the moving furnish to maintain,
or adjust for, uniformity in the lateral dimension distribution.
Each of the plurality of vanes along the lateral dimension can
be made adjustable for this purpose. For example, vane 116
shown in detail in FIGURE 7 is adjustable so that its end por-
tion 118 moves in a laterally oriented arc, with respect to the
mat being formed, by pivoting about axis 120. Adjustment
control 122 with positive lock means 124 is shown in detail in
FIGURE 8. Various adjusted positions of the plurality of vanes,
along the axial length of a distribution roll, are shown by
dotted lines in FIGURE 6.
The longitudinal dimension of distribution provided
by distribution means 82 and the longitudinal dimension of the
preselected area of deposition are correlated; preferably they
are substantially equal. In this way, the distributed furnish
moves in the forward direction through the remainder of the
processing line over the full cross-sectional area selected
and established for deposition. This substantially eliminates
furnish flow problems and also helps eliminate the introduction
of extraneous forces which can result from changing the cross-
sectional area of the flow path, or the direction of the flow
path, in approaching dep~sition.
_-n-
1 i5562~
A commercially acceptable continuous flow rate can
be maintained for lightweight fibrous furnish while allowing
adequate space and time for fiber separation and orientation.
The furnish, as discharged from the longitudinal distribution
means 82 is moving forward over the full area of intended
deposition. The uniformly distributed furnish is delivered
by the longitudinal distribution means 82 into screening
chamber 130 (FIGURE 2). A screening means 132 within chamber
130 extends over substantially the full area of deposition.
Small clusters of fibers which may remain in lightweight
fibrous furnish are separated in the screening means to deliver
discrete fibers; workable screening means are known in the
art and can include a plurality of closely spaced wires
extending longitudinally over an area at least equal to that
selected for deposition of fibrous material.
The cross-sectional area (transverse to the direc-
tion of furnish flow) of orientation chamber 140 (FIGURE 3)
is substantially equal to the area of deposition. The furnish
is deposited on a surface presented by continuously moving web
support 142. Details of a preferred electrical orientation
structure for lightweight fibrous furnish are described in
copending application Serial No. 366,762, filed December 15,
1980, entitled "Orientation and Deposition of Fibers in the
Manufacture of Fiberboard". The mat formed on support web 142
is moved into apparatus (not shown) for compaction and curing
under pressure and heat to form the end product fiberboard.
--11--
`` 115~62~
Support web 142 can be an endless belt, moving in
the direction of arrow 144, guided and driven by roll means
such as 146, 147. This forming conveyor surface is preferably
foraminous. In place of the usual bronze fourdrinier wire,
support web 142 can be formed from filament having desired
dielectric properties when electrical orientation is used;
e.g. support web 142 can be woven from nylon filament.
For purposes of reducing random dust escape from the
forming line shell when working with lightweight fibrous furnish,
the pressure can be maintained slightly negative subsurface of
support web 142 by any suitable suction means. Butterfly valves
150, 151, 152 and compartmentation can be provided to distribute
and extend a slight negative pressure to the peripheries of the
structure. A negative pressure of about 0.25" of water is
recommended to help reduce ambient dust while not adversely
affecting orientation when working with fine fibers.
Access of air to the forming line shell is provided
at a removed location, e.g. through dampers 60, 62 to avoid
possible adverse effects of incoming air on the mat. Thus, in-
rush of air as the mat exits from the forming chamber is sub-
stantially eliminated even when negative pressures greater
than recommended to reduce ambient dust are utilized. Also,
the negative pressure in chamber 156 can be adjusted to help
consolidate the mat upon or after exit from the mat forming
area. In chamber 158, the negative pressure should be strong
enough to help prevent fracture as the mat is transferred from
the continuous filament belt 142 onto belt 160 for transport to
press.
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1 1S562~
The combination of elements described moves the
furnish continuously without interruption of forward movement
through the process line with no need to rely on pneumatic
impulsion for movement of lightweight fibrous furnish.
Furnish uniformly distributed over the full area of deposition
is moved along a flow path which is normal to the area of
deposition. In working with furnish which is to be direction-
ally oriented, this flow path is provided prior to entry into
the orientation chamber 140. This permits effective orienta-
tion at commercially economical production rates of lightweight
furnishes in an electric field.
Referring to the metering section of the enlarged
view in FIGURE 3, the profiling chamber 26 establishes the
dimensions and positioning of furnish discharge which is
correlated with the dimensions and positioning of the metering
rolls 50 and 52. One of the metering rolls can be adjustably
positioned horizontally, via dotted line slot 162, to assist
in proper alignment. The metering rolls 50, 52 rotate about
their longitudinal axes 164 and 166, as indicated by the arrows
168 and 170.
In accordance with the teachings of the invention,
the metering rolls 50, 52 are formed from materials which possess
the necessary characteristics for positive gripping of the
furnish, compressing the furnish, and controlling forward move-
ment without shearing the column of material being formed and
metered through metering nip 54.
In working with lightweight pressure-refined wood
furnish, the compression ratio imposed by the metering rolls
-13-
` li55~2~
50, 52 should not be substantially greater than 4:1. That
is, the cross-sectional area of the furnish as delivered from
the profiling chamber, measured in a plane perpendicularly
transverse to the direction of movement of the furnish, should
not be greater than about four times the cross-sectional area,
similarly measured, of metering nip 54. Since one dimension
is being held substantially constant (as shown the lateral
dimension), the remaining dimension (as shown the longitudinal
dimension) is selected and controlled to effect the desired
compression. In practice, when working with the pressure-
refined wood fibers of the specific embodiment, the ratio
should be in the range of 2:1 to about 3:1.
With the selected compression ratio and metering roll
of selected characteristics, the furnish will be compressed into
the proper configuration for accurate metering and steady move-
ment without shearing of the furnish column. Selected bristle
materials provide satisfactory surface characteristics for the
metering rolls.
Moisture absorption properties should be considered
in selecting bristle materials for the metering rolls, scalping
roll, and distribution brush rolls. Furnish may be premixed
with curable resin binders which can be in liquid form. Also,
moisture content of the fibrous material can vary dependent on
ambient conditions, previous handling, and conditioning prac-
tices. By selecting bristle material of low moisture absorptionproperties, e.g. about 5% by weight or less, accumulation of
resin on the brush rolls is avoided. Polypropylene, which
exhibits moisture absorption of about 2% by weight, is preferred
-14-
1 15S62~
for this purpose. The bristle material should also be capable,
by suitable roll assembly techniques, of exhibiting other desired
characteristics.
Bristles for metering rolls 50, 52 should be short
in length, e.g. about two inches on a roll having a diameter
of approximately sixteen inches, with the bristles tightly
wound, spirally. These rolls are driven by a variable speed
drive so the RPM of the metering rolls can be adjusted to meet
mat basis weight and production speeds. The metering rolls
50, 52 rDtate at a relatively low speed, typically about three
RPM, in handling lightweight furnish.
The controlled flow of the metered furnish from nip
54 impinges on scalping roll 56 rotating in the direction shown
by arrow 172 in FIGURE 2. Scalping roll 56 rotates about its
axis 174 which is laterally oriented; axis 174 is aligned with
and substantially parallel to the axes 164 and 166 of metering
rolls 50 and 52. The surface of roll 56 should provide the
desired scalping action. Bristles, tightly wound spirally,
i.e. in a spiral or helical curve, provide the desired action.
Scalping roll 56 is rotated to provide a high surface velocity
of about 2000 fpm to 3600 fpm in a representative embodiment
working with lightweight furnish.
The distribution roll brushes rotate about their
respective axes which are laterally oriented and aligned in
parallel relationship with axes of the scalping roll 56, the
metering rolls 50, 52, and with each other. Direction of
rotation, as shown in FIGURE 3, is selected to aid uniformity
of distribution. The upper distribution rolls 83, 84 rotate
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115562~
to impose a horizontal component of motion which is outwardly
directed with relation to the triangular configuration formed
by the banks of distribution brushes, the two bottom rolls
87, 88 may rotate inwardly to prevent furnish from striking the
leading and trailing ends of the distribution chamber. The
RPM of each roll can be set to suit fiber geometry and flow
rate. The distribution brushes are preferably formed from
spaced, axially-extending, parallel, rows of bristles
distributed about their peripheries as shown in FIGURE 3.
Referring to FIGURE 1, cyclone flop gates 16, 18
are pivotally mounted and establish substantially equal flow
in both lateral directions of bidirectional screw 14 which is
driven by motor 180. Metering rolls 50, 52, scalping roll 56,
and distribution brush rolls 83-88 are supported at their
respective lnngitudinal ends providing drive connections.
Reerring to FIGURE 2, from shaker screen chamber
130, in which the shaker screen is vibrated by drive 182, a
furnish with individualized fibers passes through a drop zone
forming part of orièntation chamber 140. The fibers can be
oriented by an electrical field established by a bank 184 of
electrically conductive rods as described in above referenced
copending application Serial No. ~ G,`7G ~ .
The handling methods and apparatus taught are
applicable to furnishes including wood shavings and flakes as
well as lightweight comminuted fibrous furnishes produced by
disk refining of wood pieces. Furnishes produced by pressurized
steam refining of wood particles have, in the past, presented
difficult handling problems which impeded economical production
. 1~.
1 ~55~
rates. Therefore, while the principles taught are generally
applicable to particulate furnishes for manufacture of
composition board, specific data will be presented on what
has been considered the most difficult to handle furnish.
Pressure refined wood comprises, for the most part,
extremely fine hair-like fibers of less than one mil in
diameter, generally from about 1/4 to about 1/2 inch in length
but extending up to 3/4 inch. A significant portion by weight
comprises splinter-like pieces of varying length about 1/4 inch
to 1/2 inch; and, the remainder is dust-like. This furnish
generally exhibits agglomerating characteristics similar to
those of cotton fibers. The flow rates achieved with this
material constitute a significant contribution of the present
teachings. For example, in a representative specific embodi-
ment, in excess of 300 pounds per minute of pressure-refined
wood fiber furnish, having a bulk density of about 1-3/4 pounds
per cubic foot, can be uniformly distributed to provide a
deposition rate of about four (4) pounds per square foot per
minute over a preselected area on the support web of approxi-
mately seventy-five (75) square feet. With the forming conveyor
support web 142 moving at a linear speed of fifty (50) feet per
minute, the end product after compaction and curing under
pressure and heat, will have a thickness of 1/8 of an inch at
a density of fifty pounds per cubic foot; at a linear speed of
twenty-five (25) feet per minute for the support web, the panel
will have a thickness of 1/4 inch after compaction and curing.
Utilizing the over-feed system for continuous-flow
handling, the bidirectional feed screw will be rotated at about
115562g
fifty (50) RPM; metering rolls of sixteen (16) inch diameter
are operator controlled and rotate at about three (3) RPM;
a ten (10) inch diameter scalping roll rotates at about 750
to 1000 RPM, and sixteen (16) inch diameter distribution rolls
rotate at an average oE about 500 RPM. The operator controlled
distribution rolls can vary between 250 and about 750 RPM
dependent upon characteristics of the furnish including moisture
content. The drive motor for the shaker screen is operated to
provide cyclic vibrations for the screening wires dependent on
the materials, e.g. about 1000 per minute.
Furnish flow and uniform distribution can be provided
at forming density deposition rates determined by available
capacity of the curing and pressing facility. Where the flow
rates available with the present invention exceed available
curing and pressing capacities at a particular site, it is
preferred to utilize optimum continuous flow rates for the
particular forming line, which can exceed five (5) #/ft2/minute
for lightweight furnish; furnish deposition above available
curing capacity can be shaved off before pressing and returned
to the input side of the line.
Suitable resin binder systems using urea formaldehyde,
phenol formaldehyde, isocyanate, and tannin formaldehyde are
well known in the art as are the techniques for proper addition
of the resin and for curing.
Along with the principles of operation, physical
values such as weights of furnish handled, dimensions, configura-
tion, placement of structures, and RPM or linear movement of
various elements have been set forth in describing commercially
1155628
practical process line methods and apparatus. In the specific
embodiment shown, the lateral dimension has been described for
the initial distrlbution step while the furnish is confined in
the longitudinal direction fDr metering. In the light of this
disclosure, modificatiDns can be made in these physical values
while still relying on the principles taught. Also, while
final distribution DVer the dimensiDn in the machine forming
direction as shown is preferred, distribution over this dimen-
sion cDuld be taken up first while utilizing the principles
of metering and controlled continuous flow taught. Therefore,
in determining the scope of the invention, reference should be
made to the appended claims.
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