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Патент USA US2411542

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‘METHOD QF mklne-rmwqob TUBING
' I
7' y -r,.E.-u.cH;/r'
j _
"riled Sept. 10,"1942;~_
,3 Sheets-Sheet 1
. '
vTheodore’ Lila/I ~ I
* '
I A Tram/Ex;
Nov. 26," 1946. v ‘
2,411,542 ~ '
'r. a. ILCH '
' Filed Sept. 1o,~ 194g '
5 ‘Sheets-Sheet .2
. .,
' '-
mm“, . i
A Worm/5y; _
Patented Nov. 26,1946 '
' 3mm;
“mqwmaPLWQOP -
empsbeatLN. 1., assiznor: 1, i .,
United'states l'lywoodgorporatlon, a?oorpoi
1 .'
mummies»; loél?lirserial
<01- 1154-;11h
sentencing vvgreat strength atransverse
' The inventionvjrelatesyto lama-‘fabricated ' direction
and, therefore considerable strength in
into. the form orajpipe or tubingand more: par- - Y hoop tension, th being ideallysuited [for conticularly ‘toseamless
tubing. ,“seame v . veyirig» ?uids under considerable ,- pressure. _ The
less)’ as hereinafter used} throughout this specs. . _strength of the tubing is controlled by the vman-incation,wis intendedftoindicate the absence oi '
her, in which the grain is madejto,
extending from the
any de?nite line or juncture
' "interim; to the._exterior~surface joi ,thevplpel-,-,or
tubinghj Y
. ' plywood Qtubingl ,htI-vingv
of plywood. butewblch .
layers‘of veneer. I If-thefpreponderance of grain _
of the wood is .laid up tojrun';
?nished tubing will be preferably‘ ~ or vvalue for ‘
produce such
obisct tithe-1 invention
the inherent-advantages
of its tubular '
form has extremely valuable industrial; applica¢
tions, for instance. as. -a structural member “con-y
stituting a. stronglcolumn or, by reasonor its“
use as a column,whereas.ii the preponderance
of the veneer‘grain ismade ,to,-;run- aroundthe , '
‘.pipe, it willbemoreuseiul for carrying ?uids
‘for particular a com
pressure. I Obviously‘,
mercial applications, intermediate’. ,e?ects .01;
strength can be secured, for; instance by altering '
great‘ strength in, heoptension as alpipe icrcone 15‘ the thickness of the tubing, "or- the, number of,
veying ?uids underpressure. vA further object
veneers or which the tubing-isconstituted.
' of the,invention' is
to provldeaplywood tube . '
whose lengthis considerably greaterandin fact
may be ,many times 'greatenthanthe ‘maximum
transverse dimension orthe ‘tube, the tube‘beinz
ultimate shape, a pipe or tubing, thatis, hollow
' structures , whose length; is considerably ,_8rea_ter
built ‘up; from individual veneer, units. (It is also
an 7 objectv oi. the ‘invention
y ,
proved process for
than their diameters, by rolling vup cylindrically
torrovide an 1m:
and in succession, .ay
' plurality of layers or veneers of plywood‘which
wood tubing, wherein thefindividual veneer
‘compressive ,
are notsubjected tofany ‘peripheral
have been. suitably provided ‘with ,layers' of. .ad_
hesive, sliding the thus rolled layers or veneers
stresses .during their assembly and particularly
'' during the moldingoperation. “Other objects will
individually and. successively-‘inside v a longitudie
nallysplit steel‘ ‘mandrel of suitable length
become evident from the further, moreidetailed
,, While attempts have been madeby vprior
~ workers .to'produce amore or less seamlessplyi
. intoloose
the manufactureoisuehplye‘
description ‘or the invention. -
.In its .gbroadest aspects, myginvention-consists "
in the building up, and molding 111 its
_ ?nal
I 7 its two open
contracting the '
, 3°. split mandrelyto enable the Ilnishedarticleto -
‘ be withdrawn‘ more rea'dilyafter the'molding and .
1 after release ‘of the mandrel, insertlngai?exible
wood pipe- or tubing, for ‘instancerby assembling , ?uid-tight
;in' the shape ‘of 1a cylin-p
‘sueh'pipe ‘or ‘tubing:
a e
drical tube. inside the. assembled,’ veneers‘ within
plywood, such attemptshave not been productive. ,the steel mandrel, and‘ arter placing‘ the ‘an a
l, of -a' commerciall 'e-utilizabletubing because ‘oi: gregate of mandrel, veneeraand membrane into
the inherent stresses, characterising the material" af?uid pressure, chamber, sealing" the. aggregate '
inordinate - amount;
produced and. because an .in
therein, applying, heat, and pressure by means of
‘ _ 7
‘built-.upveneers to'vcause '
. oi'assembly
work; is invol ed
otgsuch material. )The primary "cause or failure. 40' the‘
withuwhich it has
or [such 18' pl'Q?lllct tO-take its place'in' industrial bee‘nepreviously
_ r
impregnated» or coate'd,to there!
‘ has been its de?ciency in
‘ applicationahowever,
strength Mthimthe longitudinal dires?on and
' the transverse - direction
' more. ' besides‘ the lunsatisiectorr nature '01" the
‘ product heretofore ‘produced, “the fabrication in;
volved extremely, high costs; and comparatively ‘
small production_yield.i_ v; H
> ~ .jIn accordance with‘:
invention, I bani pro;
‘by-producejthe plywood tubing.
\A particular embodiment of my ‘novel process
ofproducing a plywoodtubingandlofanap-,
. .
l I. fFisgl is a perspective view or a ‘steelmandrel, ._
or‘ split‘ tube into which the, veneers inthe carry-g
duce ‘economically .and with .egrcellent. results so. ' ingout of my. process are adaptedtobeplaced:
far as v the necessary "j characteristics oifstreng'th
1Fig'.‘2_'is a cut-"away view, also in perspective,‘
are concerned,- anxiety or sizes oi’ ‘plywood ‘pipelf ‘ '_ ‘showing the steel mandrel, the tubing’ constituted .
or tubing. in»v lengths
of a ‘plurality of, iv'enee'rs
in _osition§withln
so that these , comparatively long structures can; ' mandrel,
and the ?uid-tight; membrane or rubber
for insta'nce,‘in'" the
* befused ‘as'a strong,‘ column,
production or‘ radio§entenh§
are illustrated
suitablein ‘for
the carrying
out such process,
in '
fabric sleeve‘ within the tubing; is " "i
Fig. 3 is an end view or section showing in con
centric arrangement an outside casing with the
in position within an outer casing ll, being sub
therein by resting
stantially centrally ‘ disposed
on a cradle IS. The mandrel
split steel mandrel and its contents positioned
Fig. 4 is a cut-away view showing the mandrel,
ready for molding of the tubing therein, in posi
tion in the outside or cooking casing;
assembly is pushed
into the ‘outer casing ll until the end of, the
mandrel i0 abuts tightly against a gasket 20
Fig. 5 is a schematic showing of the outside
casing and necessary plumbing for the heat and
pressure treatment; and
Fig. 6 is a section through the outside‘casing'v
or cooker with a modi?ed sealing "arrangement
for the veneers in the split mandrel.
positioned within andbearing against the head
2! of the casing i8.‘ At the ‘other end or the outer
casing a companion plate "22, havingja gasket 23
onits inner face is pressed against the end of ‘
.the mandrel III, a plurality of bolts 24 being used
to press the companion plate 22 toward the end
‘plate 25 of the casing. The bolts “being drawn
up on theend plate, "a tightening and sealing of
Referring more particularly to the drawings,
in which similar reference characters identify " both endsor themandrel I0 is accomplished- ‘111
"this manner. the “whole of the sleeve I! of the
similar parts in the several views, sheets of ply
?uid-tight‘ or rubberized fabric is sealed, except
wood veneer coated with a suitable adhesive,‘ after;
. for an‘ aperture 26 in‘the center of the gasket
drying, are curled or rolled up cylindrically and
23 and a like aperture 21 in the gasket 20 at the
slid one after the other, into the split steel man- ' head end‘ of the casing. l8. These apertures 28
drel III which is provided throughout its length
with a slot 1H of suitable width. The sheets of
veneers are accurately templated to the proper
width so that when they are slipped into‘ the
20 and 21 are for the admission and egress of the
heating and cooling ‘?uids.
‘ >
Afterthe sealing,v thus‘ accomplished, if ?uid
under‘ pressure is admittedat one end, and the
steel mandrel, through one of'its open ends, they
end is closed thebag ‘or sleeve 15 will be
will expand against‘and completely overlie the
interior surface thereof, having ‘neither an over 26 distended, forcing the ,veneerstightly against the
interiorsurfacelof the mandrel I 0 .whilev the lat
lapping nor an appreciable gap between their ad
ter is in the transversely contracted -' condition.
Jacent free edges after they are forced into place.
If these veneers have been previously coated with
Each layer of veneers is accordingly a little nar
rower than the~preceding layer slid into‘ the 30 a heat-sensitive adhesive audit the ?uid intro
duced is sumci'e'ntly hot to activate the ‘adhesive,
mandrel. The butt joints in the several layers
the veneers will be tightly bound together. Pres
of veneers are very carefully arranged sothat
sure resulting from heating of air or generation
they do not occur at exactly the‘same ‘point in
of vapor in the-?brous layers, is relieved through
the periphery of the tubing to be formed, but are
the narrowed slot ll whichstill‘ remain'sin the
distributed at various points throughout ‘the pe
mandrel after‘ contraction,>as shown in Fig. 3.
riphery of the tubing. ‘As a'plurality of layers
After-sufilcient exposure to heat has been ob
of veneers are used for the tubing, the completed
tained, the end plate 22 can be removedand the
molded tube will be, to all intents and purposes,
split_‘tube or'mandrel can'be withdrawn from
After successive sheets of veneers have been 40 v the outside-steel casing. If the clamping device
or ‘clamps are then released, the mandrel will
slid into the steel mandrel I0 and all ‘of the piles,
spring to its normal, larger diameter, the plywood
are‘ in place, clamps i2, distributed appropriately
tube which-has been made can be withdrawn ‘and
throughout the length of the steel mandrel, are
is'ready for treatment, assembly'into useful ar
tightened by‘ the bolts i3, giving the mandrel the
or for sale without‘ further treatment.
exact inside diameter desired, and which will 45 ticles
, Describing the operations above outlined, and
be the outside diameter of the plywood tubing
referring now particularly to Fig.‘ 5,‘ when the
to be ‘produced.v The layers of veneers within
sealing, as above described, has been'completed,
the steel mandrel constitute the pipe i4 ‘and will,
air valve '28 and inlet valve v29 are opened, the
after the heat and pressure treatment herein~
valve 30 being closed. Exhaust valve 3|
after‘described, form the molded plywood tubing;
is-generally left open. Air pressure'through the
It will be understood that at the time that the
inlet ‘valve 29 is permitted \tor'enter‘ the'casing
until the pressure, asyindicated by air'pressure
mandrel is contracted, the veneers lie loosely
within the mandrel, with many and consider
gage 32, is sui?cient to cause the veneers inside
able spaces between the individual veneers and
the mandrel l0 to'snap into place. An airline's-l
between the ?rst veneer and the mandrel. The 55' sure‘o'f
approximately‘50 ‘pounds per square inch
degree of contraction ‘of the mandrel is very
found in practice'to be adequatefor this
small and is insufficient to create any peripheral
compressive forces in any of the veneers. ‘As
already indicated, the purpose of the ‘contraction
of the mandrel is to provide a slight clearance
between the same and the ?nished tube upon re
lease of the mandrel at the end of the process. ,'
A ?exible, rubberized fabric. or similar ?uide
tight membrane in the shape of a cylindrical
. tube or sleeve I5 andwhich has both ofit's ends
open, and is longer than the split steel mandrel
I0, is then slipped or threaded into the steel
mandrel within the assembled veneers, the ends
of the‘sleeve being doubled back‘for a short dis
tance over theoutside of the mandrel, as shown
at'Hi in Fig. 4, and an outer ring or sleeve-l1
is slipped on the folded back ends of the mem
brane to hold‘the fabric in place.
The mandrel‘ assembly,~ now containing thev
plywood veneers and the sleeve, is then placed
purpose. The air valve 28 is then closedand the
steam valve 33-is' opened. Exhaust valve 30 is
‘openedat the same time as the'steam valve v33;
The-steam passing into the casingthrough‘the
inlet valve 29 and inlet pipe 34 forces the air out,
the temperature rising, vas indicated by the ther
mometer 35, to approximately‘300"
The pres
. sure is maint'ained‘pu'rely by the'pressure of the
steam, or if it is desired ‘tohave thel'pres'sure
‘higher without increasing the temperature, ad
ditional air-may be admitted'through the valve
28. 'A continual draining orbleeding of the sys
tern'is- permitted through the exhaust valve III
to prevent stratification and to maintain the de
S The outside‘casin'g l8 isfprovided at a number
If points throughout itsleng'th with vents I8,
. which permitgany pressure built, up between the
outer'casing VII and thesteel mandrel ill to be
a411,, m:
bring them .tetheknnai molded» "condition by i
continuouslyrelieved. "I have mum-mamm
the activation oig-lthe glue.’ - t~
mum‘1 of two'rof these wentsaor small . holes'in'the
- ‘It win beseen'mm the mainline-that.
Iouter'casing- :i 8115-‘ desirable‘ for thelproper carry
ing out or'mirprocesspw
' r"
; *1
providedva process: for?
,tubingiwhéréilf the’tube ‘ishulltil?from a plu
' rality ot‘zpliable-veneeriunits,.wl*uchare inserted
- imparted: ‘to; the assembly-1 ‘. within "the: 'casingeto .
, one ,by: one, and 1‘ endwise, into, 'a" relatively, long,
' activate ‘the, thermo-sensitive adhesive, cooling
in, any, suitable manner‘. isie'?ected' if the adhesive ‘
longitudinally s‘plit- mandrel? the mandrel hav-"
or glue is Jathermo-plastic- adhesive. ,If the-ad; 6 {.ing substantiallythe outer-contours ‘and dimen
- ,7 hesive or glue used'is thermo-se'ttinggit is only 10 '3
' , 4_ necessary to release thel‘pressure.
oiqthel'?nished-iplywood article; and that
(in- the i-icourse v‘ofgfthe telescoping: assembly of the
Thev mandrel
:l'il'isithen removedirom‘the outer casingall; the '
ifclamps i2 loosenedf‘thé sleeve I!‘ removed, and
the ?nished ‘plywood tubing withdrawn from ‘the
‘steel mandrel l0.
The sizes of .7 plywood tubing rwhichvrmaynbe
preparatory .to the in?ation oi . the -
: ?exible {membrane : and likewise during‘ the‘ course
f'oij-the‘molding; thev veneer units'are ‘not subjected
tofany peripheralvcompressiomj. e., no vforce is
Y exerted ‘on them ; ,fromrthe-outsideto compel-them
to contract fperipherallygiethe veneer , units being
I, "fabricated in i accordance with "my" process ‘are
., atmost' subiectedvaside from the‘ radial pressure
" limited only" by theexpeclien‘cy; and = feasibilityfoi
or’ the“ ‘pressure : normal 1 vto ‘ their ‘surfaces’, to "a
handiing‘and byithe size of theapparatusu-Plye
wood tubing‘s in s‘izesranging fromr-onemalirinch .20 f'slight-peripheral vt‘ensio'm- Thereby buckling- of
.to? six;inches ‘ outside‘ :diameter ‘have
pro‘; L‘ the'iveneers is avoidédwhileatthe same time
-_ ‘v szduceduysuccessfully'Hby‘meansv of‘ the apparatus; _ --overlapping 1* at the“ 'j’oints "01'! the individual I ve-'
~and-i iniiacc'ordance ‘with :the' steps 7‘ hereinabove
ides'cribedi Apparently,‘ there 'is'n'o limit to the‘ ‘
is, ' diameterof. the tubing; except by’, convenience in z,
, handling? and in‘ the‘ sizeijof- ‘suitable apparatus.
.l.~ 'rnememod ‘of “forming ran integral molded '
iseamlessr’tubing'j=from?jilbrous sheet ‘material ,
=whi'ch comprises‘introducing'a plurality:v of. layers
‘For instance,- :plywood', tubing‘ up : to ;twenty+four
inches-i :outside diameterv ,could ."be' ‘freadilyfi-proi- '
} of g 'thermov-‘sensitive ' adhesive‘iicoated ‘sheets of I
i?brous?-ma't'erial into‘ arelatively rigid cylindrical
eleven feet- have been ‘in commerciali-ipro‘duction 180 §casing ,iunti1@.,theilayers ,are built up Tingtubular
{formv ‘against, the interior surface of . ‘such casing,
and in ‘larger diametersieven :greatertlengths can ‘ Q, :the"
layers being coiled" individually . andv intro
'duced. So far .:v as lengths are ~'c‘oneerned,~- uplto‘
I be.’ produced“ with facility," economy, iandivs'atis
duced endwise insuccessioninto-the casing,;land I
' 'factory results‘; from thepoiht ‘of view ofistrenlgthT
being» ‘allowed expand in {the casing; and yas-j
sum‘e, approximately‘ the contour loft‘. the casing,
:in both longitudina‘land vtransverse ‘directions; ' I
I J While I‘ have described hereinabove'a'speci?c
"applying ;;a tubular I membrane f interior-1y - of ‘the
‘various changes in=7the“speci?c;arrangementv of’ , . via'sse'rn-bled-sheets,v andediste‘nding; the membrane 3 v
iembodiment'iylof ‘my invention,<;itv is obvivaust-liatv
1the ‘several parts ‘of-the- apparatus imaysb'e made
without @departing'» from, ,my:' invention.- ‘ >Forjin
‘ Yby'a;heatrandfpressuré rriediurnwsuf?cient to press.’
* _ athezrsheetsjagain'st the.interior'ot*thecasing-td -
stance,“ in v‘place of. the??exible f?uid-jtight s mem
‘bond: theasheets to' ea'ch;;other and toymoldqsuch
sheets to‘ “theicon?guration- ‘of’; the casing;vv a; a
brane or sleeve "I:5‘;:open at'zb‘oth' endsvnecessitatr ' " £512.;3'I'he methodilofiiformin‘gw aninte‘gralmolded
' ing the‘ doublirigiback,‘offithe‘excess at each end, 3
there may be used a cylindrical tube very much > _ seamless plywood ‘.tubin'g" from wood veneers,
‘like-an automobile inner tube with both. ends '
sealed. ,With such‘ alternative structure,¥a valve ‘'
stem would be utilized at each end having‘ difierr-v ,
ent' sealinglmechanism ‘than that described. _-1 ‘
.In Fig. 6, I have shown in scheni'atic'crossesec- ,
‘as the layers of veneers are omitted, such
an alternative structure fQrY'attaining'the sealing
of the mandrel andveneers- _In suchalternative
which-"comprises applying athermo-s‘ensitive ad
hésive'fto‘a plurality of wood veneers, introducing ' '
I ‘I
successively narrower stripsv oi’ v‘such veneers one ,
by v*on'einto' a relatively rigid cylindricalgcasing
‘ "one end vthereof,'iapplyingy ‘an expansible,
fm‘embrane‘ interiorly of the assembled veneers,
and distending the membrane‘with, a heated me-_ > ‘
dium at a' pressure vsi'ii‘ilcientto press the veneers
outward against the interior of ‘,the casing to
old them-into 'a seamless plywood‘tube.
terial, for instance ‘rubber, such as is used'in anj '7
3.;Process"for the’ manufactureof seamless,
automobile inner
multiply tubing-of ~,cons'iderably
I greater " length
- structure, a cylindricalvpressure tube Iii‘ oima-g
‘ seams» of the tube being vulcanized, a :valve'stem
' 1H being provided ateach‘end ‘of the tube.‘ The _
> than ‘diameter, ,which'icomprises "coiling a sheetv
‘ tube ‘can then be‘ in?ated to distend the same _
ameter less than the average" outside diameter
against the layers of veneers, by'air and/or steam
. pressure admitted and exhausted‘throughvalves
42, and subsequently de?ated. “The split ,‘man-i 00
‘of ?exible materialgto an average outside‘ di
of the?nished tube, inserting the so coiled‘sheet ‘_ /
endwise into a long, relativelyrigid tubular man- v >
,dreliil, into which theveneers and ‘sleeve or tube ~' a _' drel having inside transverse . dimensions subel ,
‘stantially equal to the outside transverse dimen- , ,
v, 40 have beenplaced is supported within the outer "
' cooking casing in substantially the same manner . a
as heretofore described in ‘connection with ,the '
sions of the ?nishedtube, and allowing the coiled
' sheet to expand within thev mandreland, assume . '
a ‘tubular contour similar. to that of the mandrel
interior ‘and substantially [free irom~ pressure
Aside from the speci?c variation vJust described, .~ ' stresses
in the peripheral direction, similarly coile ‘ ‘
preterred embodiment of the apparatus.v 3 ~
other alternative forms of structure-and details‘, ‘
ingand individually. and successively'inserting
‘V will be apparent to those skilled in the art. For
the mandreliin‘ endwise fashion an addi- "
instance, while I have described‘ a speci?c ar‘-" Y‘
rangement ‘oi ’ plumbing “for the introduction of "l0 tional sheet'or sheets of. ?exiblematerial, the
7 air and steam to the ‘outer casing, it is'obvious'jv : subsequently coiled sheets being allowed to ex
pand against the previously inserted sheet within
that,vwithout departingirom my invention. other,‘ ' the
mandrel, there being ‘provided a layer ‘of ad
‘methods of ‘sealing the split steel mandrel ‘with ' ‘_ a
its enclosed sheets'of veneer may-be used for the '
fapplication- of heat and pressure to ,the'jveneers
' ‘
hesivebetween adjacent sheets, then‘heating the ‘I ‘
assembled sheets, and applying ?uid pressiu'ev
from the interior of the .mand'rel outwardly
against the so te'escoped. ?brous tubesato' cause
activation of the adhesive and mold the sheets 01'
providing, w'tubuiar mandrel and inserti’g such
temporary tubes venclwise and in succession into
the mandrel, permitting the veneers to expand
ilexible material'against the interior surface of
within the mandrel whereby they‘ assume a tu
the mandrel and into an integral multi-ply tube,
bular shape with the longitudinal edges of each
and'removing the tube from the'imandrel.
veneer tube in contiguous relation, inserting a
4.- Process for the manufacture of “ seamless
?exible ?uid-tight tubular membrane inside the
plywood tubing, which comprises coiling a wood
assembled veneers within the mandreL'applying
veneer '-.nit to an average outside diameter less ‘
heat and suillcient pressure, byineans of said
than the average outside diameter of- the?nished 10 vmembrane to the built-up veneers'to cause the
tube, inserting the so coiled unit :endwise into a
vactivation of the adhesive and thereby mold the
relatively rigid tubular mandrel having inside
assembly of theiveneers into an integral [plywood
transverse dimensions substantially equal to the
tube having external dimensions corresponding
outside transverse» dimensions of; the ?nished
to the internal dimensions of the mandrel, and
tube, allowing the coiled, veneer units to expand 15 removing the molded seamless plywood tube from
within'the mandrel and. assume a tubular con
tour smaller than that of the mandrel interior
and substantially free from pressure stresses in
_ - 6., Process for the manufacture of seamless
plywood-tubing, which vcomprises ‘cutting indlvid- '
the peripheral direction, coiling and individually
ual veneers to suitable dimensions, said veneers
and successively insertinginto the mandrel in 20 being provided upon certalnof their outer sur
endwise fashion an additionalv veneer unit .or
units, such last-mentioned individual coiled -ve
faces with a thermo-sensitive adhesive, coiling,
"in'succession, such individual cut veneers about
'a- longitudinal axis until the longitudinal edges
neer units being each allowedto expand against
the previously inserted unit-within the mandrel,
overlap, the temporary tubes thus produced being
there being provided'a, layer ‘of adhesive between 25 vof a diameter less than the?nal diameter of the
adjacent units, and then heating the veneers and
molded seamless plywood tube to be produced, in
applying ?uid pressurefrom the interior of the
serting such temporary tubes endwise, and in suc
mandrel outwardly against the so telescoped
cession, into a tubular mandrelwith theirlongi
veener tubes to cause activation of the adhesive
tudinal joints in staggered :relation, permitting
andmold the veneer aggregate against the in 30 theveneers to expand within the mandrel where
terior surface of the mandrel and into an integral
by they'assume atubular shape with the longi
multi-ply-tube, and removing the plywood tube
tudinal edges of: each veneer in contiguous rela
from the mandrel.v
tion, inserting a ?exible ?uidftight tubular
‘ 5. Process for the manufactureof' seamless‘
membrane inside the assemblediveneers within
plywood/tubing'which comprises cutting individ 35 thev mandrel, applying heat ' and pressure by
ual veneers to suitable, dimensions, applying a
means of said membrane to the built-up veneers
thermo-sensitive adhesive to said veneers, coil
to cause activation of the adhesive and thereby
ing, in succession; such individual cutzveneers
mold the assembly. oi’-'veneers into an integral
about a longitudinalraxis until the. longitudinal
plywood tube while“ venting air andvapor through
edges‘overlap, the temporary tubes thus produced 40 the mandrel, and removing the molded seamless
being o1"a diameter less than the ?nal diameter
of the molded seamless plywood to be produced,
plywood tube from the mandrel.‘
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