Note: Descriptions are shown in the official language in which they were submitted.
1,~'234~73
_S P_E_G_I_~F_I_C A_T I O_N_
_T_I_T_L_E_
"PROFILING AIRISTEAM SYSTEM FOR PAPER-MAKING MACHI~ES"
BACKGROUND OF THE INVENTION
The invention relates to improved paper-making machines
and somewhat more particularly to improved means for effective
control of cross-machine moisture profile in a traveling paper
web undergoing dewatering, as in a press section.
Prior Art
Methods and mechanisms for applying steam to aid in
dewatering a paper web are known, for example, see U. S. Patent
No. 4,272,316 or U. S. Patent No. 4,163,688.
A presently accepted theory for this technique is that
as a paper web or sheet is heated by applied steam, the viscos-
ity of water insuch web is reduced, making water removal easier.
Recent developments in this area include compartmentalized steam
boxes having separate cross-machine compar~ments allowing steam
to be selectively applied in the cross-machine direction to a
traveling web. Typically, such steam boxes are positioned about
the outer surface of a suction roll so that steam can be drawn
into th~ suction box and through the web supported by such roll.
The ability to correct or control the cross-machine moisture
profile in a web has met with various degrees of success and
problems still remain. One of such problems is that each com-
partment cannot ~e readily sealed against the surface of the
~raveling web. One reason for this is that a minimum clea~nce
of about 1" between the surface of the steam box and the suction
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roll must be malntained in order to avoid damages from wads,
wrap-ups, etc. With such large clearances, much of the applied
steam in one compartment is frlee to migrate to adjacent compzrt-
ments, with a resultant indiscriminate application of steam.
SUMMARY OF THE IN~ENTION
The invention provides a method and means which
overcomes the prior art drawbacks and provides a more effective
control of cross-machine moisture profile in a traveling paper
web undergoing moisture removal in a paper-making machine.
In preferred embodiments of the invention, a
compartmentalized system, such as in a chamber, is provided in
working relation with a tra~eling paper web undergoing dewater-
ing, as in a paper-making machine press section. This system
includes a plurality of cross-machine profiling areas of
compartments, each having valve-controlled means selectively
supplying relatively dry air and/or steam to the web area
associated with each profiling area.
In an exemplary embodiment of the inven~ion, a steam
box having a plurality of cross-machine compartments is posi-
tioned in close-running relation to a fluid-permeable means
supporting a traveling web, typically a press nip defined by
two press members, such as press rolls, one of which can be a
grooved roll or a suction roll. The steam box is provided with
a first cross-machine header, connected to a steam supply in
the paper-making machine. Exiting from such header is a plur-
ality of supply pipes and control valves, each associated with
an individual compartment of the steam box. In addition, the
steam bo~ is provided with a second cross-machine header~ con-
nected to a compressed air source in a paper-making machine,
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with supply pipes and control valves associated therewith and
with each individual compartment.
In preferred embodiments, a single valve means controls
both the steam and air flow to an individual compartment. Each
valve means can be interconnected to a computer and moisture
sensors can be associated with select transverse areas of a
traveling web and be interconnected to the computer so that the
valves are appropriately activated by the computer for steam
and/or air flow in accordance with the signal generated by the
sensors.
In accordance with the principles of the invention,
the air supply can be used to "flood" a compartment so as to
prevent cross-machine migration of steam into that area.
Selectively supplying dry air to a select compartment of a steam
box is further advantageous in that it can be utilized to con-
trol dry areas of a sheet. As air is drawn into a sheet,
evaporation cooling occurs, reducing the sheet temperature. At
lower sheet temperatures, pressing is less effective. Hence,
steam is supplied to control wet streaks in a sheet and air
supply to control dry streaks in a sheet.
Other ob;ects, advantages and features as well as
equivalent structures and methods which are intended to be
covered herein will become more apparent with the teachings of
the principles of the present invention in connection with the
disclosure of the preferred embodiments thereof in the
specification, claims and drawings, in which:
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BRIEF DESCR]:PTION OF THE DRAWINGS
FIG. 1 is a schemat:ic elevational p~rtial view
illustrating a section of a paper-making machine constructed
and operating in accordance ~ith the principles of the
invention;
FIG. 2 is another somewhat similar schematic
elevational view showing another form of the invention;
FIG. 3 is a partial somewhat schematic elevational
view illustrating a steam/air box of the invention in association
with a grooved press roll;
FIG. 4 is a partially broken-away top view illustra~ing
one form of header arrangements utilized to supply air/steam to
the airlsteam box of the invention;
FIG. 5 is an elevated detailed view cf a valve
arrangement utilized to control steam/air in the air/steam box
of the invention;
FIG. 6 is an elevated detailed view of an alternative
valve arrangement utilized in the practice of the invention; and
FIG. 7 is a schematic di.agram illustrating a working
relation between a computer, moisture sensors and respective
valve means of an air/steam box constructed and operable in
accordance with the principles of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As illustrated in FIG. 1, a newly formed web W is
carried on the upper surface of a traveling first endless felt,
Fl, for example, from a Fourdrinier machine or from a first
press section (not shown), into a psess nip Nl defined between
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a lower grooved roll 11 and an upper suction roll 12. A travel-
ing second endless felt F2 is guided by guide rolls (not shown),
so as to sandwich the web W between the felts Fl and F2 as they
pass through the press nip Nl. At the press nip Nl, water is
removed downwardly into the grooved roll G and from there to a
saveall in a conventional manner. On the off-running side of
the nip Nl, the web W adheres to the second felt F2 as this felt
travels around the suction roll 12 in the manner shown. The
first felt Fl is guided away fro~ the press nip Nl by a suitable
guide roll and back through its endless loop in a conventional
manner. The second ~elt F2, carrying the web W on its outer
surface, travels around the suction roll 12 and past the suction
gland 13 as illustrated. A profiling steam/air box 15 is posi-
tioned in close working relation with the o~ter surface of the
suction roll 12 so as to feed air or steam to select areas of
the web via a controlled valve 15a connected to a steam source S
and to an air source A. The supplied steam and/or air streams
penetrate through the felt F2 and into the web W and thence into
the suction gland 13 of the suction roll 12 to effect tempera-
ture control of the associated areas of the web. A plain-
surfaced press roll 14 is positioned above suction roll 12 so as
to define a second nip ~2. A third endless traveling felt F3
is guided over the surface of the plain press roll and against
the web W so as to sandwich the web between the felts F2 and F3.
The so-sandwiched we.b is then carried away for further process-
ing, for example, to another press section or to a dryer
seetion of a paper-making machine.
FIG. 2 shows another press section wherein the
profiling air/steam box of the invention is advan~ageously
employed. In the embodiment here illustrated, a newly fo-rmed
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web W is carried on a top surface of a first endless felt Fl
into a first press nip Nl defirLed by an upper plain roll 23 and
a lower grooved roll 22. Just prior to the press nip Nl, a
compartmentalized profiling airlsteam box 21 is positioned in
close running relation with the felt Fl so as to selectively
feed steam and/or air upwardly through the felt Fl and into the
web W via control valve 21a. At this location, steam aids water
re~oval while dry air retards water removal so that steam can
be supplied to control wet streaks in the newly formed web or
sheet and air can be supplied to control the dry areas thereof.
After the press nip Nl, the felt Fl carries the web W into a
second press nip N2 defined by a lower plain roll 24 and an upper
suction roll 25 having a suction gland 25a. On the off-running
side of the nip N2, the felt Fl is guided awa-; from the web W
back through its endless run via a plurality of guide rolls
(not shown). The web W continues to adhere to the outer surface
of the suction roll 25 because of the suction gland 25a. A
second profiling air/steam box 26 is positioned in close running
relation with the outer surface of the suction roll in close
conformity with the suction gland 25a and selectively feeds air
or steam against the web surface via control valve 26a. Heated
water is more readily withdrawn from the web via the suction
gland whereas cooled water (cooled by supplied air) is somewhat
more difficult to withdraw so that control of wet and/or dry
streaks in the web W can be readily accomplished. A second
endless traveling felt F2 is guided around a further plain press
roll 27 positioned to define a further press nip N3 with the
suction roll 25. On the off-running side of the nip N3, the
felt F2 carries the web W on its undersurface away for further
processing as desir~d,
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The profiling steamjair boxes of the invention, such
as boxes 21 ~nd 26, correct cross-machine moisture profiles in
webs undergoing dewatering. Each steam box is relatively fluid
impermeable except for an open front face and is divided into a
number of compartments in the cross-machine direction. Cross-
machine headers are provided to supply compressed steam and air,
respectively, to each compartment, which also includes an
individual control valve. As is ~own, paper-making machines
typically include a source of pressurized steam and may include
a source of pressurized air. In any event, relatively dry air
can be supplied from an external source by a fan or other suit-
able means. A select air stream can be used to flood a compart-
ment to prevent cross-machine migration of steam into the
flooded compartment. Further, such dry air stream provides a
means of controlling dry areas of a sheet since as air is drawn
into a sheet, evaporation cooling occurs reducin~ the sheet
temperature, making water removal less efficient. In this
manner, dry areas can be controlled and by selectively applying
steam to other areas, wet streaks can be controlled.
Referrin8 to FIG. 3, a grooved roll 35 having a
plurality of grooves 35a is shown positioned in working relation
wlth a profiling and/or steam box 30. The box 30 is provided
with a back wall 31, an upper wall 32, a lower wall 33 and a
forward open face 34, along with appropriate end walls (not
shown), all joined to~ether in a relatively fluid-tight manner
so as to be able to direct the steam and/or air flow toward the
front face 34 of the bo~ 30. The walls are preferably formed
from sheet mPtal and a plurality of individual compartments, for
examp?e, a~out 6'l in width, are provided along the cross-machine
di~ection of the box. For this purpose, a plurality of
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compartment walls 31a, 31b, 31c, etc. are suitably secured
between the upper and lower wal:Ls 32 and 33 of the box, as s~own
at FIG. 4. Each compartment is provided with a control valve 40
suitably interconnected with an air supply A and a steam supply
S. The air supply is connected with an air feed line 43 and the
steam supply is connected with a steam feed line 45. The valve
means 40 include a hollow body 42 and a valve stem 41 which
carries a double-truncated conical valve body 44 mating with
respective valve seats 44a and 44b. Valve seat 44a is formed at
the upper portion of valve body 42 while valve seat 44b is formed
within the steam pipe 45. By selectively moving the valve stem
41 either the valve seat 44a can be shut while valve seat 44b
can be opened, as shown in FIG. 5 or the steam may be moved
upwardly to shut the steam supply pipe by blocking valve seat
44b while opening the air supply valve seat 44a. As best seen
at FIG. 4, the compressed air source and steam sources are
respectively connected to headers which interconnect with the
respective valve means associated with each compartment. The
valves are so positioned away from the front face 34 that a
pressurized stream of air/steam cannot directly impinge on a
surface adjacent the open face.
FIG. 6 shows an alternate embodi~ent of a control
valve useful in the practice of the invertion. As shown, a ball
valve 40a is provided for connecting the steam feed pipe 45 with
the box 30 and with the air feed line 43. Movement of the valve
stem 41a allows either steam or air to flow through the valve
housing into the steam box 30.
Referring now to FIG. 7, a portion of a web W is
shown travelinr, in the machine direction M and extending in a
cross-machil direction CM of a paper-making machine~ A
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plurality of moisture sensors Sl, S2, S3, S4, e~c. are positioned
in working relationship with the web W and the steam/air box 30,
with each sensor associated with a select cross-machine area of
the we~. ~ach sensor senses the moisture level in its given
area of the web and generates a signal which is fed to an oper-
ational computer. The computer is electrically connected to a
plurality of solenoid-operated valves 40b, each associated with
a given compartment of profiling box 30. In this manner, in
accordance with the signal received from the sensors, the
computer opens or closes valves 40b to admit steam or relatively
dry air to the particular compartment.
Thus, it will be seen that we have provided an improved
method and apparatus for more effective control of the cross-
machine moisture profile of a paper web, particularly in
conjunction with a press section of a paper-making machine which
meets the objectives and advantages above set forth and
accentuates moisture removal in wet areas of a web while
retarding water xemoval in dry areas thereof.
