Note: Descriptions are shown in the official language in which they were submitted.
~PPARATUS FOR FO~MING BOUND--LAYER S~EET OF PAPER
~ hls inventlorl rel~tes to an appara~us for the
5 formatlon of a bound-layer ~heet of paper.
A~ bound-layer ~heet p~p~rmaklD~ m~chines, the
FourdrinlQr machln~ and th~ cylirlder machine ~ncl thelr
comblnation~ axa known to the art.. The~ pape~makincJ
m~chlne~ are chi,efly u~ed for tha manuf~cture of whlte
1 O bo~rds and 1 in~r~ D The common requlrements any ~uch
paper 1~ expected to fulflll, therefor~, lnclud~ tldy
orlentatlon of flber~, excellent :Eormal:lon and unlform
thlckn~, small local v~rlatlon o~ paper w~ight~ and
~trong adh~3~ ion b~tween comporlent lay~rs o~ th~ sheet.
15 In vi~w of th~ r~quirements ~ the bound-layer Four~rlnl~r
machine proves to be ideal among oth~r typi~s o~ paper-
maklng machine~ " Thi~ i~ b~3causs th~ adop~.ion of the
Fourdrlnl~r machlne permlt~ th~ ~heet Pormlng speed
and the feed1ny ~pe~d of dilu~e flber~water ~lurry to be
~0 ad~u~ted over a falrly wlde range ~nd, therefore, ensure~
formatlon o~ a bound-layer ~heet o~ high quallty, In
reallty, how~ve!~r, these papermaking machine~ have be~n
u~ed only for tha m~nufacture of high~ grade whlte board~
and very ~01dom ~or the manuieacture o low-priced bc)ard~ O
~5 ~hl~ i~ not mer~ly because ths lnltlal co~t o~ e~uipm~nt
~nd t~le cost of operatlon are hlgh but al80 becau~e the
bound~layer sh~!~t produced by ~uch machines hA~ a di~
advan kage in th~at the interl~y~r adhe~ iv~ 8 trength is
-- 1 --
~ . J`~ ~
~91(~
rather low.
A Fourdrinier p~permaklng machlne whlch ov~rcom~s
th~ drawbacks mentloned abo-/-eF namely, which 1~ capable
Ol' forming a hlghly deslrable ~h~et and produclng boar(l~
S of all colors, h~ been propo~d in Japane~e Pa~nt
Publication Sho 55~1980~-8640 (JapnnE3~e Patent No~
1,0~9~ 068) O
Thls lnventlon rela~e~ to lmprovement~ in and
10 Concerrling the propo~ed Fourdr~nler papermaking machlr
mentioned above~ Speclf~cally~ lt provlde~ an apparatu~
for form~ng a bound^-l~yer 3heet of papex~ whlcll enable~
drainaq~3 of water ~rom th~ layer~ of dllute f iber~wat~r
~lurry to proce~d quickly and ef~lclently~ avold~
15 induclng di~lntegration of pap~r layer~ ~ and produce~
high grade paper layer~.
In the propo$ed Fourdrini~r papermaklng machine
m~ntloned above ~ th~re ls pro~ided an endless wir~
æcxeen belt w~hich has a straight portlon used for the
20 fc~rmatlon of a papexmaklng layer ~nd al~o ha~ a fc:rming
roll rotatably di~po~ed at the leading end of the
~traight portion~ An endle~s fe~t belt having .~ pre-
llmlnarily draln2d papermaklng layex ~herlng to the
lower ~urfac6~ thereo~ :Is introduced between th2 afore-
25 mentloned ~orming rvll and endle~ wlre ~cr~en belt.While ~he formlng roll i~ rota~ed b~r the endle~s felt
belt ancl the endle3s wlre x~r~en belt~. the paper layers
one ~ach on the endle~æ wire ~creen b~lt atld the endle~.
-- 2 ~
7S
fel-t bel-t are pressed agains-t the periphery of the ro-ta-ting
forming roll. Thus, -the fibers of -the paperma~ing layers
are caused -to inter-twine and the wa-ter in the papermaking
layers is drained by centrifugal force, with -the result
that a bound paper layer is formed. At -the time that -the
endless felt bel-t is forwarded and brought in-to contac-t
with -the forming roll, the forming roll rota-ting at a high
speed entrains air and entraps it between -the forming roll
and the fel-t belt, -thus inducing disintegra-tion of -the paper-
making layer. To cope wi-th -this disadvantage, -the present
invention has groove means formed on the periphery of the
aforementioned forming roll. These grooves means permit
the aforementioned entrapped air to be expelled when the
felt belt is pressed by the endless wire screen belt agains-t
the periphery of the forming roll. Consequen-tly, disinte-
gration of the papermaking layer is precluded even when
the machine is operated at alhigh speed.
More particularly, the present invention provides appa-
ratus for the formation of a bound-layer sheet of paper,
comprising, a wire screen belt and a felt belt for receiv-
ing therebetween a firs-t paper layer upon the wire screen
belt and a second paper layer upon a first surface of the
felt belt, a forming roll rotatably disposed in contact
with a second surface of the fel-t belt, and defining there-
with a wedge-shaped gap, for comprefsing -together the first
and second paper layers between -the felt belt and the wire
screen belt for forma-tion of the bound-layer sheet oE paper,
and groove means defined within the outer surface periphery
of the forming roll, the groove means having a predetermined
spacing or pitch defined be-tween successive grooves as viewed
- 3~
in the axial direction of the forming roll for permi-t-ting
the escape o:E air entrapped within -the wedge-shaped gap
formed between the felt bel-t and the forming roll so as
to preven-t the transmission of -the air into the felt belt,
-the second paper layer, and the bound-layer sheet of paper,
and for simultaneously preven-ting -the transmission of any
excess water con-tained within the Eirs-t and second paper
layers through -the felt belt and the forming roll whereby
the excess water.is expressed outwardly away from the form--
ing roll -through the wire screen belt only, when -the bound~
layer sheet of paper is formed as a result of the com-
pression together of the firs-t and second paper layers.
The present invention will become more readily apparent
from the following disclosure of an embodimen-t of the inven-
tion with reference to the accompanying drawings, in wh.ich:
FIG. 1 is a schematic overall s-tructu:ral diagram of
an apparatus for the forma-tion of a bound-layer sheet of
paper.
FIG. 2 is a schematic diagram of a conven-tional appara~
tus for the formation of a bound-layer sheet of
, - 3a -
O~d5i
paper ~.
FIG~. 3 1~ an enlarged cross~ectlorla:l v:Lew of the
es~ent.~al part of an app~ratus embodyil~g -the presentirlvention
for the formation of a bound~layer ~heet of p~per~
E~I~. 4 ls ~n enlarg~d p~3~sp~ctiv~ view lliu~tratlng
~he es~ential part of the ~pp~ratu~ embodyin~ -th~ pr~sen-t
in~entlon ~or the :~ormatlorl o~ a bound~layer ~h~et of
p~per ~,
DET~ED DESCRIPTION OF P~EFERRED EMBODIMENT a
E~y way of lntroductlony the conventlonal Fcsurc~rlrller
papermaking m~cl~ e wlll be de~cr:Lbed wlth reference to
FIGD 1 and F:lG. 2~D An ~ndles~ wlre ~creen belt 1 ha~ a
~traight p~per~layer forming zone la ~or forming a
papermaklng layer Pl thereorl and ~a~ R form,ing roll ~
15 rotatal:)ïy dl~pos~d at the l~ading end of the paper-layer
~orming xone la. An endle~ felt belt 3 is dl~posecl ~to
travel ~ubi3tantlally p~rallelly ~c~r ~ htly obliquely
upwardly or downwaxdly~ r~lativ~ to the endle~ wir~
3cr~e~ bel~ l. Thli~ ~ndles~ fe1t belt 3 p to th~ low~3r
~0 ~urace oiF whlch the pap~rmak:Lng ~ayer P2 formed in the
s;heetformlng d~rice of the precedlng ~tag~ and prellml~
narily dralned h~ be~3n applled ~ 19 lntroduced b~tween
the ~ormlng roll 2 and tha endl~ wlre ~cxeen be1t l.
Con~equently, the ~orming roll 2 ls rota~ced by the
25 endle~ felt belt an~J posslbly~ addl tic~nally by the
endle~ wlr~ ~areen belt and, at th~3 ~ama tlm~, the
papermaklny layer~ Pl, P~ ar~ ~up~rpo~ed t pinched b~tween
the felt helt .l and the wire 3creerl belt 1; and passed
q ~
upwardly over about one fourth to one half of the entire
periphexy of the forming roll 2. The endless wire
screen belt 1, owing to its tension, presses the two
papermaking layers Pl, P2 against the periphery of the
forming roll 2, or more precisely against the felt belt
3 covering the forming roll 2. By this pressure coupled
with the centrifugal fol-ce generated by the rotation of
the forming roll 2, the considerable amount of water
contained chiefly in the freshly formed papermaking
layer Pl is drained through the meshes in the en~less
wire screen belt 1. Then, the wire screen belt 1 and
the felt belt 3 which have departed from the forming
roll 2 are passed over a couch roll 4, with the inner
surface of the wire screen belt 1 in direct contact with
the couch roll 4. The ~elt belt 3 to the lower surface
of which the two paperma~ing layers P'2 (Pl ~ P2) have
been transferred is forwarded to a press part P or to
the forming roll in the subsequent papermaking device.
The wire screen belt 1 is returned back to the straight
paper-layer forming zone la.
In this machine, the centrifugal force of the
forming roll 2 increases and the efficiency of removal
of water ~rom the papermaking layers is enhanced in
proportion as the sheet forming speed increases.
Further since -the application of pressure to the paper-
making layers and the drainage of water from these
la~ers continues throughout the period during which the
wire screen belt 1 and the felt belt 3 travel around the
~90~:~7~
forming roll and consequently keep the forming roll in
rotation, the fibers of the two papermaking layers Pl,
P2 are intertwined fast along their i~terface and the
paper which is produced as these papermaking layers are
dried by being passed through the press part and the
dry part does not su~fer from layer separation. This
machine features these and other merits.
The actual operation of this machine, however, has
revealed the following problems. Since the forming roll
2 is a smooth roll or plane roll having a cylindrical
surface as its periphery, air is captured in a wedge-
shaped gap 6 formed between the felt belt and the forming
roll 2 at the time that the felt belt advancin~ toward
the forming roll comés into contact with the forming
~ roll/ and the entrapped air, unable to find a way out,
is lodged within the felt belt. At the time that the
wire screen belt l with its own tension presses the two
papermaking layers Pl, P2 against the periphery of the
forming roll, this lodged air is forced out of the felt
belt and transferred into the papermaking layer P2.
Consequently, the air leaves its mark in the bound-layer
wet sheet and induces the so-called phenomenon o~ dis-
integration of sheet. The produced paper, therefore,
suf~ers from impaired quality.
In an effort to overcome this drawback, the
inventors have trially constructed a forming roll by
stretching a net round the periphery of a cylinder cell
so as to expe:L the entrapped air through the meshes of
-- 6
the net into the interior of the roll. Although this
arrangemen-t succeecled in precluding disintegration of
sheet, it has a disadvan-tage in that part oE the water
in the papermaking layers which ought to be expelled
outwardly by the centrifugal force of the forming roll
is absorbed by the felt and is gradually accumulated
inside the roll to the e~tent of impairing the efficiency
of water removal. When the sheet forming speed is low,
the water which has thus accumulated within the roll ma~
be discharged in the axial direction from the opposite
ends of the roll. When the speed is high, such discharge
of the water cannot be obtained. This accumulation of
water, therefore, deprives the device of its characteris-
tic feature, namely that the efficiency of water removal
increases with the increasing sheet forming speed. Thus,
the device must be operated at a low speed~ When the
plane of the felt belt tangent to the peripher~ of the
forming roll forms a small angle with the horizon, the
water contained in the roll is forced out into the wedge-
shaped gap between the felt belt and the forming roll andabsorbed in the felt belt before the felt belt comes into
contact with the roll. At the time that the wire screen
belt with its own tension presses the papermaking la~ers
Pl, P2 and the felt belt against the periphery of the
Eorming roll, the water is squeezed out of the felt belt
and transferred into the papermaking layer P2. Thus,
disintegration of sheet is brought about not by air but
by the water forced out of the felt belt. Moreover,
because oE its peculiar construction, the roll having a
net stretched round the periphery thereof can not be
easily formed with perfect circularity o-f shape. Thus,
the device suffers from poor dimensional accuracy and
the net must be replaced after a certain length of
operation. The price of this device is notably high as
compared with that of a roll made of a steel tube.
The inventors, therefore, have made a diligent
study in search of a measure which retains the charac-
teristic features of the conventional machine intactand, at the same time, precludes the entrapment of air
in the wedge-shaped gap 6 between the felt belt and the
forming roll. They have consequently ascertained that
when the forming roll is provided on the periphery
thereof with circular or helical grooves, disintegration
of sheet is precluded and the air entrapped is smoothly
expelled. _
The grooves 5 thus formed on the periphery of the
forming roll 2 fulfill their function fully when they
have a depth of 2 to 3 mm and a width of 1 to 3 mm.
When these grooves 5 are formed in a circular shape,
they may be spaced in the axial direction of the roll at
intervals of about 2 to 3 mm. When they are formed in
a helical shape, they may be formed with a pitch equalling
the interval.
When grooves 5 are formed circularly or helically
on the periphery of the forming roll 2 in accordance
with this invention, the entrapped air is allowed to
escape through these grooves 5 at the time tha-t the felt
belt 3 is pressed by the wire screen belt against the
periphery of the forming rollO The felt belt 3, there-
fore, does not en-train any air and disintegration of
papermaking layers due to the entrapped air can no longer
occur. Since the grooves have a narrow width as mentioned
above, the water contained in the two papermaking layers
is hardly allowed to enter the grooves at the -time that
the felt belt is pressed against the periphery of the
forming roll. Thus, the provision of these grooves
results in substantially no degradation of the efficiency
of removal of water from the papermaking layers.
The forming roll is made of a steel tube or stainless
steel tw~e 0.7 to 1.8 m in outside diameter. Optionally,
the steel tube may be covered with a layer 7 of rubber 10
to 20 mm in thickness~ The grooves may be Eormed on the
periphery of the roll by the use of a lathe. The grooves~
therefore, can be formed easily at a rather low cost.
As is clear from the ~oregoing description, this
invention improves the bound-la~er Fourdrinier papermaking
machine by the provision of circular or helical grooves
on the periphery of the forming roll. Owing to this
improvement, disintegration of papermaking layers is no
longer suffered even when the machine is operated at a
high speed and the papermaking layers are bound with ample
adhesive strength to afford high-qualit,y paper. The
improved machine offered by this invention can be used for
the manu~acture of not only high~grade white boards but
also boards of ordinary grade.
g
