Note: Descriptions are shown in the official language in which they were submitted.
APPARATUS FOR LAYING A MAT OF WOOD STRANDS
This Invention relatss to the manufacture of
a composite produci- of wood strands such as waferboard.
Most specifically the Invention provldes an apparatus
for laylng wood strands In a mat of uniform th1ckness.
The term wood strands includes wood wafers,
flakes, partlcles and chlps havlng a length equal to or
greater than the width, and havlng a thlckness not
greater than 3 mm (1/8 Inch). Wood strands for compo-
slte panelboards are generally made In lengths of from
12 mm (1/2 inch) to 76 mm t3 Inch) widths of up to 38mm
(1-1/2 Inch) and a thlckness not greater than 3 mm.
In the preparatlon of waferboard, wood wafers
are first blended wlth resln and wax and then lald 1n a
mat of unlform thlckness on an advanclng conveyor whlch
conveys the mat to a hot press for curlng the resln to
make a waferboard product. The wafers are generally
lald In several layers one on top of the other. in
some cases certaln layers have ~he strands orlented.
In one case the two outer layers have the strands orl
en-i-ed In -i-he lengthwlse directlon of the board and the
Inner layers hava the strands randomly orlented. Other
types of waferboard have the strands orlented along the
length of the board In some layers and across the width
of the hoard In other layers.
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~L7~2~3
At the present time, the maximum length of
wafers In the preparatlon of waferboard has been not
greater than 76 mm (3 inch)~ However, there is con-
sideratlon today of produclng a waferboard wlth wafer
lengths of 305 mm (12 Tnch) or longer. Such a board has
greater strongth propertles than exlsting waferboard.
Waferboard utillzes more of a tree than plywood and
thus Is a more efflclent use of wood. Furthermore, the
wa1ght of waferboard ~ade from long wafers 1s substan-
t1a11y the same as the we1ght of a plywood havlng
equlvalent strength properties.
Although the applicat1on is prlmar11y con-
cerned w1th warerboard, other types of wood strands may
be used w1th the apparatus of ths present Invention.
The composlte product may 1nc1ude external veneer
sheets w1th wood strands 1n between, the wood strands
may be la1d tn an orlented pat~ern.
It is the purpose of the present lnventlon to
provlde an apparatus for 1ay1ng wood strands up to at
least 305 mm 1n length In a mat of substant1ally unl-
form th1ckness. The wood strands may ba lald In an
orlented pattern or In a random pattern, The apparatus
spreads the wood strands In a unlform manner to provIde
a mat havlng substantlally even thlckness.
The present Inventlon provldes an apparatus
for contlnuously laylng wood strands In a mat of sub-
stant1ally even thlckness, the mat advanc1ng at a
substantlally constant speed, comprlslng means for
formlng a plle of wood strands of substantlally uni~orm
depth, a plurallty of splke rolls rotatlng about sub-
stantlally horizontal, parallel axes spaced vertlcally
apart and located at one slde of the plle of wood
strands, the splke rolls adapted to pull wood strands
out of the plle and form a unlform curtaIn of falllng
strands, advancing means for the pile of wood strands
to force the plle agalnst the spike rolls, a palr of
counter-rotating spreader rolls, side by slde In the
same horizontai plane, -ihe spreader rolls havlng axes
substantially parallel to the spike ro r I axes and
located beneath the splke rolls to recelve the curtain
of fallTng strands, each of the spreader rolls havlng a
plurallty of radlally extendlng spTkes to dlstrlbute
the strands evenly In a mat beneath, and horlzontal
adjustment méans for the spreader rolls to adjust the
locatton of the spreader rolls beneath the curtain of
falllng strands, and provlde a predetermlned dlstance
between tlps of the splkes on one spreader roll and
tlps of the splkes on the other spreader roll.
In a preferred embodlment the means for form-
lng the plle of wood strands Includes a rake back
conveyor located at the top of the pile to convey wood
strands at the top of the plle away from the splke
rolls, and wher01n the advanclng means Includes a
conveyor at the bottom of the plle to advance the plle
towards the splke rolls. The splke rolls are prefer-
ably located between the rake back conveyor at the top
of the plle of wood strands and the conveyor at the
bottom of the plle, the axes of the splke rolls are In
a substantlally stralght llne sloplng upwards towards
the rake back conveyor. The preferred angle of slope
is in the range of about 55 to 60 degrees to the horl-
zontal.
In another embodlment an orlentlng means Is
located baneath the spreader rolls and above the mat to
provlde an orientatlon of strands In the mat. In one
embodtment the spike rolls adjacent to each other have
splkes wh}ch intermesh and overlap, or alternatlvely
the spikes are In Itne9 and a space Is provlded between
tlps of the splkes on one spike roll and tlps of the
splkes on the adjacent spike roll~ The spikes on the
splke rolls and on the separatlng rolls, In one
embodlment are formed from flat strlps havlng a
rectangular cross-sectlon.
In drawings which illustrate embodlments of
the Invent5On
- Flgure 1 is a slde elevatlon showlng one embodlment
of an apparatus for laylng a mat of wood strands
accordlng to -the present Inventlon.
- Flgures 2 and 3 are schematlc partial elevatlons
showlng different conflguratlons of the arrangement
of splkes on adjacent splke rolls.
- Flgure 4 Is a partlal Isometric vlew of a splke roll
or a spreader roll havlng one type of splkeO
~71~2~
Referrlng now to the Flgure 1, th0 formlng
apparatus lO has a bin 11 with a top entrance 12~ The
wood strands pass through the top entrance 12 to form a
plle 13 whlch rests on an apron conveyor belt 14. When
the strands enter the bin 11 they pass through a rake
back conveyor 15 whlch rakes the top of the plle 13
backwards in such a manner that the level of the pile
Is maintalned at substan-tlally the same helght as it
advances on the apron belt 14. The rake back conveyor
15 moves wood strands backwards and the apron belt 14
moves the plle 13 forwards.
At the end of the apron belt 14 and between
the apron belt 14 and the rake back conveyor 15 are a
pluralIty of spike rolls 16. The spike rolls 16 have
horizontal parallel axes whlch extend In a substantl-
31 Iy straight line sloping backwards towards the rake
back conveyor 15. The dlstance between each splke roll
Is sutflclent so that radial spikes 17 extendTng radi-
ally from the splke roll 16 gently puli the strands out
of the plle 13 -to meter the flow of strands, and form a
unlform curtaln of falllng strands whlch drop onto two
spreader rolls 18 located slde by slde In the same
horlzon-tal plane, and wlth axes substantlally parallel
to the axes of -the splke rolls 16. A space is provlded
between the spreader rolls 18, the space belng In the
approxlmate center of the curtaln of falllng strands,
Some s-trands fall through the space between spreader
rolls 1~. The two spreadar rolls 18 are counter rota-
tlng so that the ~ood strands that fall on the spreader
rolls 18 are thrown outward of each roll 18 and fatl In
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~7~
a substantlally even layer to form a mat 19 restlng on
a mat conveyor 20. The speed of the apron belt 14 and
fhe rota-i-lonal speed of the spike rolls 16 can be in-
dependently var1ed to control the flow of strands.
Each of the spreader rolls 18 has a pluralIty
of radially extending splkes 21 to aid Tn distrlbutlng
the strands In a mat havlng an even th1ckness. As
shown in Flgure 1, each of the spreader ro`lls 18 is
mounted on a trunnlon block 22 which has a horizontal
movement, and a threaded rod 23 and lo~king nut 24
provlde adjustment for each spreader roll so that a
predeterm!ned space can be provlded between tips of
the splkes 21 on one spreader roll 18 and tips of the
sp1kes 2t on the acijacent spreader roll 18. Further-
more, the spreader rolls 18 can be positioned an equal
distance apar-i- from the centar of the falling curtaln
of strandsO The rotatlonal speed of the spreader rolls
18 can be adjusted to ald tn the even distribution of
the strands. These adjustments are necessary to take
into account different lengths and dimenslons of wood
strands belng formed in a mat. The strands fall onto
the mai 19 from both sldes of ihe spreader rolls 18 and
through the space between the spreader rolls 18.
In one embodlment, an orlentlng devlce Is
provlded so that as the strands fall from the spreader
rolls 18, they are orlented elther In the longltudlnal
dlrectlon of the movlng mat or crosswise across the
mat. There are varlous types of orlentlng devlces
sultable for orlentlng strands. Such devlces Include
rotatlng discs, vlbratlng plates and eiectrostatic
orlenting systems.
In one partlcular orlentlng devlce, a serles
of plates 30 are hung vertlcally by wlres or cables 31
In line and spaced across the mat conveyor 20 to form
an orlenting grld. The spacing of the plates 30 is de-
pendent on the size of the wood strands. The elevation
of every other plate 30 is hlgher than the adjacent
plate to avoid the strands brldglng across the plates
30 and a vlbratlng mechanlsm 32 vlbrates the plates 30
as they hang from the strands 31 to ensure that strands
do not get hung up on the plates when falllng from the
spreader rolls 18.
In operation, wood strands drop through the
rake back conveyor 15 into the bln 11 restlng on the
apron belt 14. The helght of the plle 13 Is determlned
by rake back conveyor 15 whlch ensures that the plle Is
at a substantially even height when advanclng to the
splke rolls 16. The apron belt 14 always moves slowly
so that the plle 13 is pushed agalnst the splke rolls
16, and the splke rolls then gently pull the wood
strands from the plle 13 and meter the flow of strands
falllng In a unlform curtaln on and between the spread-
er rolls 18. The spreader rolls 18 throw the wood
strands on elther slde where, If an orlentlng devlce Is
provlded, the strands are orlented and then lald onto a
mat 19 on a mat conveyor 20. The mat conveyor 20 Is
contlnuously movlng and the mat 19 Is formed wlth a
substantlally unlform or even thlckness. Flgure 1 11-
lustrates the mat 19 being lald directly on a conveyor~O. However, If several layers are formed, the mat can
be laid dlrectly on a prevlous mat.
Figure 2 illustrates two adjacent spike rolls
16 wlth splkes 17 In line, A space is provlded between
tips of the spikes 17 on one spike roll 16 and tips of
the splkes 17 In the adjacent sptke roll 16. Flgure 3
illustrates two adJacent splke rolls 16 wlth splkes 17
Intermeshed so that the sptkes 17 on one spike roll 16
overlap the splkes 17 on the adjacent roll; It has b0en
found that for long wafers less breakage occurs In the
wafers when the splkes 17 are arranged in line, however
a better coefficient of variatlon in the resulting mat
19 occurs when the splkes 17 are intermeshed. In as
much as there Is no overlapplng of the splkes 22 In the
two spreader rolls 18, it does not matter if the splkss
In one roll are In line or In between the splkes on the
other roll.
One type of roll, either splke roll 16 or
spreader roll 18 Is shown in Flgure 4 wherein a roll
40, mounted on a shaft 41 has a serles of splkes 42
whlch are formed from flat strlps having a ractangular
cross-s~ct!on wlth th0 flat face in llne wlth the roll
axls. The flat splkes 42 are attached to the face of
the roll 40~ One method of attachlng the splkes 42 to
the roll 40 Is by angle sectlons 43 extended axlally
along the face of the rotl. Four, slx or elght splkes
42 may extend radlally around the roll, splkes may ba
staggered In radlal extenslons wlth four or six splkes
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~7~23
42 In one circumferentlal piane and the same number in
an adJacent plane but offset.
Tests were carrled out for formlng a mat in a
formlng llne 1.2 meters wide uslng an apparatus similar
to that shown In the figure. The strand flow rate waS
set at 45 kgfrnln representlng the strands fed into the
bin 11 and the mat conveyor 20 speed was 18.3 m~min.
As shown ln Flgure 1, f1ve splke rolls 16 were provTded
and speeds of 110, 180 and 215 rpm ~ere used for the
splka rol 1s7 The angle of slope of the sprke roll axes
was varled from 55 to 60 d0grees to the horizontai,
sloplng back towards the rake back conveyor 15. Spa-
clng between the splkes 17 on the splke rolls 16 was
20 cm and the splkes 17 on adjacent splke rolls 16 were
Intermeshlng wlth slx rows of splkes per row and an
overlap of 7 cm. The diametar of each spike roll 16
was 40 cm and each splke 17 extended 10 cm from the
surface of the roll. The splkes 17 were made from flat
strlps 2 cm wlde. The spreader rolls 18 were accordlng
to tha conflguratlon shown In Flgure 4, tlp to tip of
the sptkas 21 was 30 cm wlth the length of each splke
21 7 cm.
When the llne had settled down and was run-
nlng contlnuously, a sample collectlon board 1,220 mm
long and 1,320 mm wlde was placed on the mat conveyor
20 and run under the formlng apparatus of the present
Invent1On. The collectlon board was dlvlded Into ten
equal slze compartments S10 x 264 mm for long strands
(305 mm) and twenty equal slze compartments 305 x 264
_ 9 _
~7~ 3
mm for shorter strands (152 mm). After each run the
welght of wafers In each compartment was weighed to the
nearest .1 of a gram. Four runs of the shorter strands
and eight runs of the longer strands were measured for
each test condltlon givlng 80 indivldual sample welghts
per test condltlon,
In the fIrst tests wood strands 305 mm long
were run wlth the spreader rolls 18 havlng a separation
of 38.1 and 49.5 cm gap between splkes 21. The spreader
roll speed was 215 rpm. The spike rolls f6 rotated at
215 rpm also and had a spike roll axes slope angle of
60 degrees. The apron belt speed was 0.6 m~min. After
each run the we7ght of wafers In each compartment was
welghed to the nearest ~1 of a gram. Elght runs were
measured for each test condltion of the long strands
glving elghty Indivldual sample welghts'per test c.ondi-
tlon. Table I shows the overall mat weight coefflclent
.
of varlatlon for elghty measurements and the mean of
flve coefficlents of varlation calculated for each of
flve columns measured In direction of movement of mat
belt 200
TABLE 1.
._ _ ____
Slope of Splke Roll Axes _ . _ ,
to Horlzontal, degrees 60 60
Splke Roll Speed, rpm 215 215
Spreader Roll Separation, cm 38.1 49.5
Mat CoeffIclent of
Varlatlon, %
Overall 14.1 18.2
Along Mat 11.9 10.9
_ _ _
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~7~2~
Slmllar t0sts were run wlth wood strands of
152 mm t6 Inch) In length uslng a collection board wlth
20 equal compartments 305 x 264 mm In slze. Rasults of
the tests are shown In Table llo
TABLE ll.
__
Slope of Spike Roll Axes _
to Horizontal, degrees 60 60 60 55
Splke Roll Spaed, rpm 180 120 215 215
Spreader Roll Separatlon,cm38.138.1 38.1 38.1
Mat Coefficient of
Varlation, %
Overall 18~7 12.611~5 14.8
Along Mat13.3 8.4 9.4 11.2
L
Orientatlon tests wara run with 76 mm grld
spaclng with the setup as shown In the figure. The
grid was set at a helght of 38 mm above the mat belt
20, measurements were taken after the llne was runnlng
contTnuously wlth 152 mm long wood strands belng formed
Into a mat. Mean wafer orlentation angle obtained was
8.9 degrees and the orlenting grid was able to hancila
the 45 kg/min flow rate of the wood strands in these
tests. Thls orlentatlon angle Is consldered to be a
hlghly orlented product. Further tests were run wlth
152 mm grld spaclng for wood strands 305 mm In length.
The mean wafer orientatlon angle obtalned was 9 degrees
whlch Is consldered a hlghly orlented mat.
Varlous changes may be made to the apparatus
shown wlthout departlng from the scope of the present
Invantlon which Is llmlted only by the followlng claims
