Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~8S~S
The invention relates to paper machine press sections
and somewhat more particularly to an arrangement which conveys a
new web from a forming surface to dewatering press nips defined
by non-suction press rolls which are capable of higher nip pres-
sures and includes felts eliminating any open draws in the ini-
tial web path so as to convey the web through at least two press
nips in a completely supported manner while permitting easy re-
moval of broke.
Prior Art
Many paper machine web transfer and press arrangements
are known. However, with increased modern-day high capacity paper
machines capable of running at speeds in excess of 3000 to 7000
feet per minute and producing webs having a width in excess of 200
to 400 inches, presently known arrangements exhibit various draw-
backs such as insufficient web support, insufficient dewatering
capacity, inability to withstand the high-speed operational envi-
ronment, inability to uniformly dewater a web, requiring excessive
suction and/or energy, requiring excessive machine space, requi-
ring excessive felt lengths, improper roll alignments for effi-
cient web txavel, etc.
For example, U. S. Patent No. 2,694,347 issued November
16, 1954 to Lloyd Hornbostel, suggests certain press sections
which are useful at slower machine speeds. The press arrangements
suggested by this reference rely on suction press rolls for ade-
quate dewatering capacity. However, suction rolls are incapable
of withstanding high nip pressures, are costly to produce and
operate and are not well suited for high-speed operations.
U. S. Patent No. 2,732,772 issued January 31, 1956 to
Lloyd Hornbostel, illustrates yet anothér prior art web transfer
and press arrangement wherein dewatering at the various press nips
occurs primarily through suction press rolls. Such arrangements
are expensive to manufacture and operate and have insufficient de-
watering capacity at modern-day speeds.
~068525
U. S. Patent No. 2,~69,437 issued January 20, 1959 to
Lloyd Hornbostel et al, suggests yet another press srrangement
which, while an improvement over the then existing prior art,
nevertheless utilized numerous suction press rolls and involve one
or more of the aforesaid drawbacks. Further, such suction rolls
are subjected to corrosive environments and limit the allowable
nip pressure which may be safely used, especially on wide web
machines.
Other prior art web transfer and press arrangements are
also known, for example, typical prior art arrangements are shown
in U. S. Patent No. 1,930,104 issued October 10, 1933 to William
H. Millspaugh; U. S. Patent No. 2,204,446 issued June 11, 1940 to
Harry C. Robinson; U. S. Patent No. 2,386,584 issued October 9,
1945 to Earl E. Berry; U. S. Patent No. 2,764,068 issued September
25, 1956 to Tom Sutherset; U. S. Patent No. 3,198,696 issued August
3, 1965 to Edgar J. Justus; U. S. Patent No. 3,268,390 issued
August 23, 1966 to Donald E. Ely; U. S. Patent No. 3,285,806 issued
Nov~mber 15, 1966 to Edgar J. Justus and Dennis C. Cronin; U. S.
Patent No. 3,315,637 issued April 25, 1967 to James E. Taylor; U.
S. Patent No. 3,355,350 issued November 28, 1967 to George E.
Reynolds; U. S. Patent No. 3,595,745 issued July 27, 1971 to Dennis
Callahan; etc. These arrangements have one or more of the drawbacks
set forth above, especially in combination with high speed, wide
web paper machines.
The invention provides an improved web transfer and press
arrangement useful with high speed, wide web paper machines. A pre-
ferred arrangement of the invention includes a first felt which
picks up a web from a forming surface, such as a wire, and conveys
a web through at least two non-suction press nips. A second felt
contacts the web prior to the first press nip, which is defined by
an upper plain grooved press roll and a lower controlled crown
grooved press roll. The two felts sandwich the web and provide a
double-felted, double-vented first press nip which is operable
at extremely high nip
--2--
10~8S25
pressures. After the first press nip, the second felt is guided
downwardly away from the web and subsequent press nips so that any
broke can be directly dumped from the arrangement without requiring
machine shutdown or movement of any machine components. A suction
transfer roll is positioned downstream of the first press nip and
guides the first felt with the web on the undersurface thereof to
a second press nip, defined by an upper plain grooved press roll
and a lower plain-surfaced press roll. The second press nip is a
single-felted, single-vented dewatering nip and after such second
nip, the first felt is guided back to the forming surface while the
web adheres to the outer surface of the plain-surfaced press roll
and is carried thereby to a further means for processing the web.
In certain embodiments, such means include a third press nip de-
fined by a plain-surfaced press roll and a controlled crown grooved
press roll. In embodiments which include a third press nip, a
third felt contacts the web prior to the third nip and passes
therewith through such nip and then away from the web. The third
press nip is also a single-felted, single-vented dewatering nip.
After the third nip, the web is guided through a first open draw
and then to a dryer section or the like. In certain embodiments,
the controlled crown grooved press rolls may be replaced by a plain
grooved press roll and/or the plain grooved press roll may be re-
placed by a controlled crown grooved press roll, depending on the
economies of the situation.
It is a novel feature of the invention to provide press
sections which are capable of adequately and economically proces-
sing wide webs at high operating speeds while achieving high water
removal and sheet tweb) quality, normally associated with heavily
loaded suction press nips but without suction so as to provide
lower capital and operating costs without sacrificing capacity
and/or quality.
It is a further novel feature of the invention to provide
non-suction press nips defined by at least one grooved roll, which
. . .
10685Z5
may be plain or be provided with a controlled crown means in com-
bination with either another grooved roll or a relatively large
diameter plain-surfaced press roll having a sheet or web release
surface, such as composed of granite, acrylic resin or other soft
or hard plastic material compositions. Press nips of the inven-
tion which are defined by a pair of grooved rolls are double-felted
and double-vented while press nips defined by a grooved roll in a
plain press roll are single-felted and single-vented so that the
sheet or web is protected and supported during the various press
nips by felts and no open draws occur in the initial web path.
FIG. 1 is a somewhat schematic side elevational view
illustrating an embodiment of a web transfer and press arrangement
constructed in accordance with the principles of the invention;
FIG. 2 is a somewhat similar view of another embodiment
constructed in accordance with the principles of the invention;
FIG. 3 is a similar view of yet another embodiment con-
structed in accordance with the principles of the invention; and
FI~. 4 is a somewhat similar view of a further embodi-
ment constructed in accordance with the principles of the invention.
The structural elements of a paper machine embodying the
principles of the invention are shown schematically as has grown
customary in the paper machine art and mechanical expedience for
supporting and driving the rolls and associated machinery will be
fully apparent to those versed in the paper making art and to
which the present invention pertains. Similarly, paper machine
elements which provide a practical working overall paper machine,
such as web forming sections or dryer sections, etc. have been
omitted or only partially shown for the sake of simplicity but such
elements will be fully apparent to those versed in the paper mak-
ing art.
In the description and claims which follow, reference is
made to on-coming or upstream and off-running or downstream direc-
tions and it will be understood that reference is made to the
106852S
machine direction, which in the drawings runs from left to right.
The invention provides a compact, high-speed, high-
capacity web transfer and press arrangement useful at modern-day
high operating speeds in processing wide webs. Press arrangements
constructed in accordance with the invention provide a double-
felted, double-vented first press section which may be operated at
extremely high nip pressures, well above allowable nip pressures
of prior art plain press roll-suction roll press couples, particu-
larly on wide web machines. Suction rolls are only used in the
instant press arrangements to effect positive sheet or web trans-
fer. In accordance with the principles of the invention, any nip
pressure (psi) reduction which may result from double-felting is
offset by the available nip pressure (pli) so as to achieve a much
dryer sheet going into a second press nip. The double-felted first
press nip substantially eliminates two-sided water removal at the
first press nip where most of the changes in the sheet quality
occur. In preferred embodiments where a controlled crown grooved
press roll forms a part of the first press nip, the controlled
crown roll allows an operator to select optimum nip pressure for
the grade of paper being produced.
A suction transfer of the sheet after the first press nip
is provided to positively transfer the sheet to a single-felted,
single-vented second press nip where higher unit pressures are pro-
vided to further dewater the sheet to yet a higher dryness level.
Thereafter, the sheet is transferred to a plain press roll and
either to a third, separately felted, Venta-Nip press (a registered
trade mark of Beloit Corporation for presses utilizing at least one
grooved roll such as described in U. S. Patent No. 3,198,697 issued
August 3, 1965 to E. J. Justus), or to a dryer or other means for
further processing the web. The third press nip may be provided
as a final water removal step within the press section so as to
provide a sheet having a maximum dryness level and a maximum mois-
ture uniformity throughout the body thereof. Any broke from the
--5--
1068525
second or third press nip is readily guided into a pulper or the
like located below the press section without requiring a broke
conveyor or means for accumulating broke.
In a paper machine such as partially illustrated at FIG.
1, a web W is formed at a forming section (not shown) on an endless
travelling wire 11 (such as in a conventional Fourdrinier forming
machine), which passes over and partially wraps a couch roll 12
(which may be a suction couch roll if desired) and then a turning
roll 13 in a conventional manner. The wire run between the couch
roll 12 and the turning roll 13 is designated as a pick-up run lla
and is preferably angled about 15 to 60 in an upward or downward
direction so that the direction of web travel does not change ex-
cessively as it is removed from the wire 11 at the pick-up run lla.
A travelling endless looped first felt F-l, sometimes
designated as a transfer felt, is guided over a pick-up roll 12
having a suction gland 14a therein and into close running relation
with the web W on the wire along the pick-up run lla. The pick-
up roll 14 urges the felt F-l against the wet web W on wire 11 and
effects transfer of the web from the wire to the felt via the suc-
tion gland 14a. A save-all 14b is positioned in close proximity
to the off-running side of the suction gland 14b of pick-up roll 14
so as to substantially prevent droplets of water and the like from
being thrown out of the roll perforations back on the top side of
the felt F-l and thus effect possible re-wetting of the felt F-l
and/or further re-wetting of the web W carried thereby. The felt
F-l is guided away from the pick-up run lla and along a generally
horizontal run as shown, although this felt run may be slightly
inclined or declined, depending on the position of subsequent press
rolls and other machine elements of a paper machine. The horizon-
tal felt run generally terminates at suction transfer roll 17.
Endless looped felts comprise natural, synthetic or acombination of natural and synthetic fibers formed into felt loops
of suitable size and water absorption characteristics and are
~0685ZS
trained over a plurality of guide and stretcher rolls. Such felt
loops are arranged for conveying and protecting a web as it travels
through a paper machine and for receiving water from the web as it
is expressed or otherwise removed from the web via various elements
of the paper machine. After the web is removed from a felt, the -~
felt may be passed through suitable felt conditioning, cleansing
and drying means of the type generally well known to those versed
in the art and, accordingly, which are not shown herein.
As the web W travels downstream with the felt F-l and in
contact with the outer or undersurface of the felt F-l, a second
felt F-2, sometimes designated as a press felt, is brought up be-
neath the web W and into supporting contact with the web by a guide
roll 7. The web W is thus sandwiched between the felts F-l and F-2
as it travels into a first pxess nip N-l. The second felt F-2 pro-
vides additional water-receiving means and aids in handling heavier
webs so as to prevent such webs from separating from the outer or
undersurface of felt F-l. If desired, the second felt F-2 may be
heated, as by steam, prior to contact with the web W so as to ren-
der the felt F-2 more water-receptive and improve the transfer of
water from the web to this felt. Typically, the felt F-l and felt
F-2 are of a felt weight in the range of about 2 to 5 ounces per
square foot.
The sandwiched web is carried by felts F-l and F-2 into
the first press nip N-l which is defined by a press couple compri-
sed of rolls 15 and 16. In preferred embodiments of the invention,
the press roll 15 may be provided with a plurality of circumferen-
tial grooves 15a, preferably of the type taught by E. J. Justus in
the aforementioned U. S. Patent No. 3,198,6~7. The press roll 16
may be provided with a plurality of circumferentially extending
grooves 16a and in preferred embodiments, roll 16 may also be pro-
vided with a means 16b ox selectively adjusting the roll crown
thereof, which is preferably constructed in accordance with the
principles taught by E. J. Justus in U. S. Patent No. 3,276,102
3S25
issued October 4, 1966. For the sake of simplicity and in accor-
dance with common usage, press rolls similar to press roll 15 will
be referred to hereinafter and in the claims as a "plain grooved ~
roll" and press rolls similar to roll 16 will be referred to here- - --
inafter and in the claims as a "controlled crown grooved roll".
An operator may selectively activate the controlled crown grooved
roll to provide a select nip pressure at the nip N-l in accordance
with the grade of paper being manufactured. Thus, the nip N-l may
be operated at uniform and extremely high nip pressures, well above
those of a present-day Venta-Nip (a registered trade mark of Beloit
Corporation for a grooved press roll shell of the type taught by
E. J. Justus in the aforementioned U. S. Patent No. 3,198,697)
press, which may be comprised of a plain grooved roll and a suction
roll combination. In certain other more economical embodiments -
where the full potential benefit of controlled crown grooved rolls,
taking into consideration machine speed, machine width, paper grade,
required nip pressure, etc. is not required or not justified in
relation to the cost of such controlled crown grooved rolls, such
rolls may be replaced by plain grooved press rolls.
Since the web W is sandwiched between the felts F-l and
F-2 as it passes through the nip N-l, the nip is referred to here-
inafter as a "double-felted nip". Further, since both press rolls
15 and 16 are grooved rolls which are vented to atmosphere, the
nip N-l is also referred to hereinafter as a "double-vented nip".
Accordingly, the nip N-l is a double-felted, double-vented nip
which may be designed to operate at extremely high nip pressures.
Any reduction of nip pressure (psi) resulting from double-felting,
is readily offset by the available nip pressure (pli) so as to
achieve a much drier sheet or web being fed to a second press nip.
Further, by eliminating suction rolls and their auxiliary equip-
ment, a substantial savings is realized in capital outlay and in
operating costs. In addition , a double-felted, first press nip
substantially eliminates two-sided water removal from the web or
1068S25
sheet at such nip, where most of the changes in sheet quality oc-
cur. Water expressed at the nip N-l is carried away from the felt-
web-felt structure via the grooves in rolls 15 and 16, respectively.
As the sandwiched felt-web-felt structure passes beyond
the nip N-l, a suction transfer roll 17 and a guide roll 7a posi-
tioned within the loops of the respective felts F-l and F-2 combine
to guide the felts and web in a substantially straight line path
which is tengential to the outer peripheries of rolls 15 and 16.
This effectively prevents rewetting of the felts and/or web by
water within rolls 15 and 16. Auxiliary equipment, such as wipers,
savealls, doctors, etc., may be associated with the rolls 15 and 16
to assist in water control and to prepare the individual roll sur-
faces for renewed intake of water.
The guide roll 7a is wrapped by felt F-2 so as to guide
the felt downwardly and away from the web and remaining press nips
of the arrangement and through its endless loop via a plurality of
guide rolls such as 7b, 7c, etc.
The felt F-l wraps the suction transfer roll 17 and the
web W adheres to the outer surfaces thereof with the aid of suction
gland 17a within roll 17. It will be noted that the suction gland
17a extends a distance substantially equal to the lower up-running
quadrant of roll 17. This effectively transfers the sheet or web
W from the felt F-2 and allows the web to undergo an approximately
90 change of travel direction without departing from the felt F-l.
The felt F-l and web W then continue travelling in a sub-
stantially straight-line path upwardly to a second press nip N-2.
In preferred embodiments of the invention, the press nip N-2 is
defined by a plain grooved press roll 18 within the loop of the
felt F-l and a relatively large diameter plain-surfaced roll 19,
positioned outside the loop of the felt F-l. The plain grooved
press roll may be of the type described earlier and the plain-
surfaced roll 13 is of a larger diameter than either of the grooved
rolls 15, 16 or 18 and has a smooth outer surface composed of a
material having web or sheet releasing characteristics and is
`"106~35ZS
preferably selected from the group consisting of granite, acrylic
resin and other natural or synthetic, soft or hard compositions,
which for the sake of economy may be provided as roll covers on an
economical roll core. The nip N-2 may be termed a single-felted,
single-vented Venta-Nip (a registered trade mark of Beloit Corpor-
ation) second press nip which is capable of producing higher unit `
pressures to further dewater the sheet or web to a higher dryness -
level. If desired, the press roll 18 may be a controlled crown
grooved press roll of the type described earlier. After the nip
N-2, the felt F-1 continues to travel upwardly in a substantially
straight-line path to guide roll 8a and then to wrap the guide roll
8a and travel back through its loop via a plurality of guide rolls
such as guide roll 8b, etc.
The web W adheres to the outer surface of the plain-
surfaced roll 19 becuase of its more dense surface in relation to
the felt F-l. In the embodiment shown at FIG. 1, the web remains
in contact with the plain-surfaced roll at least until the roll sur-
face carries the web to a third press nip N-3. As the web W enters
the nip N-3, it is contacted on its outer surface by a third felt
F-3, sometimes designated as a press felt. The felt F-3 travels
through an endless loop on a plurality of guide rolls, only one of
which is shown, i.e. guide roll 9a. The nip N-3 is preferably de-
fined by a controlled crown grooved roll 21 and the plain-surfaced
press roll 19. In preferred embodiments, the roll 21 includes a
plurality of circumferentially extending grooves 21a along the
outer peripheral surface thereof and a shoe means 21b for selective-
ly providing an adjustable crown to roll 21 and a select amount of
nip pressure on the web. However, in other embodiments the roll 21
may comprise a plain grooved press roll of the type earlier des-
cribed. The nip N-3 is also a single-felted, single-vented press
nip and provides a final water removal station for the web and
results in a maximum dryness level of the web and maximum moisture
uniformity within the body of the sheet or web. In order to mini-
--10--
' ' . ': ' ' '
10t;~352S
mize machine space requirements, the second and third press nipsN-2 and N-3 respectively, are spaced apart about 45 to 120 on
the periphery of a common plain-surfaced press roll Auxiliary -`
equipment, such as wipers, savealls, doctors, etc. may be associ-
ated with rolls 18, 19 and/or 21 to assist in water control and to
prepare the individual roll surfaces for renewed intake of water.
After the nip N-3, the felt F-3 is guided tangentially
away from the surfaces of rolls 19 and 21 as well as away from the
web W, which continues to adhere to the surface of the plain-
surfaced roll 19 for a short distance and is then guided across a
first open draw 22 and to a means for further processing of the
web, such as a plurality of dryer drums D. A draw roll 23 is pos-
itioned to contact the web in the open draw area and provide sup-
port therefor as an aid in preventing undue fluttering or the like.
A felt DF, sometimes designated as a dryer felt, is guided via roll
24 into contact with the web so as to support the web in its ser-
pentine path of travel over various dryer drums. Of course, if
desired, the dryer section may be displaced by other processing
means, such as a smoothening press or other means.
The felts passing through the various press nips, i.e.
F-1, F-2 and F-3 as well as their respective guide rolls are so
arranged as to provide an unobstructed open space B which extends
at least below the suction transfer roll 17 and plain press roll
19 and allows any broke or the like to be readily dumped through
the open draw 22 and into a pulper (not shown) located in the base-
ment without requiring machine shut-down or the movement of any
machine elements or accumulation of any portion of the broke. A
doctor blade l9a is mounted in working relation with the down-
running surface of roll 19 and prevents the web or any portion
thereof from following around the roll 19, which might cause oper-
ational problems. The doctor blade separates any broke or the like
from the surface of roll 19 in the event of web breakage and dumps
it into the open space B. It will be appreciated that at high
--11--
-- 1068525
machine speeds, any web, especially a wide web, will produce a
considera~le volume of broke in a relatively short time period and
that considerable time may be required to correct the problems
which cause the broke and to re-thread the web. The felt and press -
roll axrangement shown allows any desired amount of broke or the
like to be quickly and permanently removed from the paper machine
without movement of any machine components.
It will be noted that as the web W travels from the for-
ming section through the press section and into, for example, the
dryer section in the arrangement illustrated at FIG. 1, the "wire ~
side" of the web, i.e. that surface of the web which was in direct ~`
contact with the forming surface, is successively pressed or
smoothened at the various press nips, particularly nips N-2 and
N-3, against smooth_surfaced press rolls to remove any wire or the
like markings therefrom.
The arrangement illustrated at FIG. 2 is somewhat simi-
lar to that of FIG. 1 so that like elements are designated with
reference characters similar to such elements in FIG. 1, except
that they are in the 100 series. Thus, a web W is formed on a -
forming section which may be comprised of a pair of endless looped
foraminous forming wires 111' and 111" which are trained over suit-
able guides and dewatering means (not shown) so as to receive web-
forming stock therebetween, dewater such stock sufficiently to
form an insipient web at least by the time the wires reach a couch
roll 112. Further details of such forming section may be obtained
from U.S. Patent No. 3,726,758 issued April 10, 1973 to J.D. Parker
et al. Of course, ot~er forming sections may also be utilized.
As shown, a wire turning roll 113a positioned opposite
the couch roll 112 is at least partially wrapped by both wires 111'
~ -12-
~` -` 1068~525
and 111~ so as to protect the insipient web during the change of ~-.
travel direction that occurs at that point. The suction gland 112a
of couch roll 112 extends from a point just prior to the contact ~ -
- 12a -
-` ~06~3SZS
point thereof with roll 113a to a point just downstream thereof so
as to effectively transfer the web W to the outer surface of wire
111'. The other wire 111" wraps roll 113a and is guided via a
plurality of guide rolls, such as roll 113b, back through its loop
in a conventional manner. Wire 111' continues to travel in a down-
wardly angular direction to a turning roll 113c which, in combina-
tion with other guide rolls, effectively guides wire 111' through
its loop.
The web W is transferred from the outer surface of wire
111' along the pick-up run lla by a first felt F-101 which is
guided into close running web transfer relation with the wire 111'
by a pick-up roll 114 which has a suction gland 114a to cause the
wet web W to follow the felt F-101 and travel therewith along a
substantially horizontal run into a multi-nip press section.
The basic arrangement of this press section is substan-
tially similar to that shown in FIG. 1 and reference is made to
that discussion for a more detailed explanation of the various el- ~ -
ements.
One important difference between the arrangements of
FIGS. 1 and 2 is that in FIG. 2, the suction transfer roll 117
within the loop of felt F-101 is positioned so as to be in nip-
defining relation with the plain-surfaced press roll 119. In this
manner, the suction transfer roll 117 is lightly nipped against
the surface of the plain-surfaced press roll 119. In this manner,
the suction transfer roll 117 is lightly nipped against the sur-
face of the plain-surfaced press roll 119 and prevents blowing or
the like thereby insuring more positive web or sheet control. In
addition, this type of arrangement is somewhat more compact than
that shown at FIG. 1 and requires less machine space. `
In the embodiment illustrated at FIG. 3, elements simi-
lar to those in FIGS. 1 and 2 are designated with identical refer-
ence characters, except that they are in the 300 series.
Generally, the basic arrangement of this press section
-13-
S~S
is, at least through the nip N-302, substantially similar to that
shown in FIG. 1 through nip N-2 so that the reader may refer to
that discussion for a more detailed explanation of the various
elements.
One important difference between the arrangements of
FIGS. 1 and 3 is that in FIG. 3 the third press nip N-303 is de-
fined by an upper plain-surfaced press roll 339 (which may be sub-
stantially similar to rolls 19 or 319) and a lower controlled crown
grooved press roll 346 (which may be substantially similar to rolls
16, 21 or 316). In such an arrangement, the sheet side opposite to
the side in contact with roll 319 is pressed to remove any objec-
tionable surface maxkings or the like therefrom. In addition, this
form of a third press nip, i.e. nip N-303, is provided with a felt
F-303 along the bottom thereof for easier water removal as well as
providing a second pressing operation on the bottom of the web
(rolls 315 and 318 provide a pressing operation on the top of the
web and roll 316 provides a first pressing operation on the bottom
of the web). In this manner, the sheet obtained from an arrange-
ment as shown in FIG. 3 is of somewhat higher quality.
The arrangement illustrated at FIG. 4 is somewhat simi-
lar to that of FIGS. 1, 2 and 3 so that like elements are designa-
ted with similar reference characters, except that they are in the
400 series. As can be seen, the basic arrangement of this press
section is, at least through nip N-403, similar to that shown in
FIG. 2 so that reference may be had to that discussion for a more
detailed explanation of the various elements and their functions.
One important distinction between the arrangements of
FIGS. 2 and 4 is that in the arrangement of FIG. 4, only two press
nips, N-401 and N-402 are utilized. This arrangement is thus
suited for the production of certain paper grades which do not
require a third press nip to yield sufficiently dry high quality
paper.
The web transfer and press arrangement of the invention
-14-
.
~0~8~'~S
is capable of high speed operation and of satisfactorily handling
wide webs with a uniform removal of substantially more water there-
from than possible with more conventional suction rolls. Further,
the capital outlay and operating costs of such an arrangement are --
considerably lower because of the elimination of larger suction
rolls, vacuum pumps and other associated equipment. In addition,
the substantially imperforated rolls utilized in the various press
couples in the illustrated ar~angement are substantially impervious
to the corrosive environment typically found on a paper machine and
may be safely loaded to nip pressures substantially above those
available with perforated or suction rolls. Accordingly, the web
transfer and press arrangements constructed in accordance with the ~ `
principles of the invention are exceptionally suited for modern-day
wide paper machines.
The basic press arrangement provided by the invention is
extremely versatile since the first, second and, where desired, the
third press nips thereof may be respectively defined by an upper
plain grooved press roll and a first grooved press roll, a relative-
ly large diameter plain-surfaced press roll and a second grooved
press roll, and the plain-surfaced press roll and a third grooved
press roll. In one variation of the press arrangement provided by
the invention, the first, second and third grooved press rolls may
comprise plain grooved press rolls; in another variation the first,
second and third grooved press rolls may comprise controlled crown
grooved press rolls; and yet in another variation the first, second
and third grooved press rolls may comprise press rolls selected
from the group consisting of plain grooved press rolls, controlled
crown press rolls and mixtures thereof. Similarly, the basic press
arrangement may be readily converted to a three nip or a two nip
structure as desired without undue difficulty. Each of these
variations have an economical and/or functional advantage and pro-
vide a user thereof with an option of converting from one variation
to another without requiring a complete restructuring of the basic
`` 10~525
press arrangement.
The drawings and specification present a detailed dis-
closure of certain preferred embodiments of the invention, and it
is to be understood that the invention is not limited to the spec-
ific form disclosed, but covers all modifications, changes and
alternative constructions and methods ~alling within the scope of
the principles taught by the invention.
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. . - . . : ~ . . . . .
