Note: Descriptions are shown in the official language in which they were submitted.
lOSSZ90
This invention relates to a machine and process
for the production of a material in web form, particularly
paper, from a suspension of fibers in water.
As is known, various types of paper making machines
5. and processes have employed a breast box which receives a
stock suspension via a feed line and which delivers the stock
suspension onto a water permeable element in layered fashion.
Further, in some cases, as described in British Patent Spec-
ifications 1,129,757 and 1,329,409, it has been known to
10. feed air or gas into the stock suspension to form a foam con-
taining finely distributed air bubbles. On the one hand,
this improves the quality of the resulting paper while, on
the other hand, there is a considerable energy saving, since
smaller quantities of water are circulated in the paper ma-
15. chine. In order to form such foams, special mixing deviceshave been provided in the feed line at a relatively consider-
able distance from the breast box. However, since there is
a risk of the air bubbles separating out in the feed line and
in the breast box, special stabilizers and emulsifiers have
20. to be added to the water used for forming the stock suspen-
sion. These agents render the process expensive and are
undesirable in the finished paper or web material. For this
reason, these gas injecting processes have not been accepted
on a widespread scale.
25. Accordingly, it is an object of the invention to
provide a process and a machine by means of which it is possi-
ble to form a water and gas mixture in a stock suspension
without the use of stabilizers and emulsifiers.
It is another object of the invention to prevent
30. separation out of gas bubbles mixed into a stock suspension.
2. ~,4
105SZ90
Briefly, the invention provides a machine and a
process for the production of paper in which gas bubbles can
be mixed into a stock suspension and maintained therein prior
to formation of a paper web.
5. The machine comprises a feed line for delivering a
flow of stock suspension from a suitable source, a water per-
meable element for receiving the stock suspension in layered
form, a breast box and a mixing means for forming fine gas
bubbles in the stock suspension. The breast box is connected
10. to the feed line for receiving the stock suspension and for
delivering the suspension onto the water permeable element.
The breast box also has a turbulence means for agitating the
stock suspension. This turbulence means includes a plurality
of parallel suspension ducts each of which has at least one
15. step-like widening. The mixing means ,~ncludes at least one
gas duct which leads into each of the suspension ducts for
supplying gas into the stock suspension in the suspension
ducts.
The process includes the steps of generating a
20. stock suspension of fibers in water, passing the suspension
into a turbulence zone within a breast box to agitate the
suspension, adding gas in the form of fine bubbles to the
suspension at a mixing station within the turbulence zone
and then passing the gas-impregnated suspension through an
25. outlet of the breast box adjacent the mixing station to a
water permeable element. The mixing in of the air bubbles
near the outlet precludes separation of the gas bubbles from
the suspension before reaching the outlet and ensures that the
stock suspension leaves the breast box with the required content
30. of gas bubbles without any need to use stabilizers and emulsifiers.
1055Z90
It has been found that a turbulence means construc-
ted in the above manner is particularly suitable for the pres-
ent purpose because, one the one hand, intensive turbulence
and uniform distribution of the gas in the form of small
5. bubbles in the stock liquid are ensured while, on the other
hand, a uniform distribution of the fibers in the suspension
flow is obtained.
Suspension ducts of the kind having step-like widen-
ings are known per se, for example, from German Auslegeschrift
10. 1,220,247 and U.S. Patent 3,725,197. In both cases, these
suspension ducts are intended for intensive turbulence and
hence to render the stock flow in the breast box uniform and
to give a uniform distribution of the fibers for paper pro-
duction in the entire flow.
15. The gas duct may be connected to that section of
the suspension duct which has the smallest cross-section.
This ensures a certain distribution of the gas in the stock
liquid flow before the flow reaches the first step-like
widening. In addition, the negative pressure formed by the
20. flow of stock liquid in the suspension duct can be used to
supply the gas.
The gas duct may alternatively lead into the sus-
pension duct at the entrance end of a step-like widening.
In some cases, it may be advantageous to introdu~ the gas
25. directly into the turbulent zone where mixing takes place.
Finally, it is possible to connect at least two
gas ducts to the suspension duct which are situated diametric-
ally opposite one another in one line. The air flows which
are then directed in opposition to one another can improve
30. the mixing of the air with the stock liquid.
1055290
These and other objects and advantages of the in-
vention will become more apparent from the following detailed
description and appended claims taken in conjunction with the
accompanying drawings in which:
5. Fig. 1 illustrates a partial sectional view of a
paper machine according to the invention showing a breast box
and part of a water-permeable element taken on line I-I in
Fig. 2;
Fig. 2 illustrates a plan view of Fig. l;
10. Fig~ 3 illustrates a control diagram of the paper
machine with the parts shown in Figs. 1 and 2;
Fig. 4 illustrates a partial sectional view of a
detail of Fig. 1 and showing another embodiment of the breast
box with the mixing device; and
15. Fig. 5 illustrates a view taken on line V-V in
Fig. 4.
Referring to Figs. 1 and 2, a breast box 1 of a
paper machine not shown in detail is used to form a paper
fleece on a water permeable element such as a machine wire 2
20, extending over a cylinder 3. The wire 3 may extend in known
manner along various dewatering devices to a point where the
web of paper formed from the fleece is lifted off and passed
onto subsequent processing.
The breast box 1 is connected via a stock or feed
25. line 4 to a device for generating and storing a stock suspen-
sion, which contains fibers finely and uniformly distributed
in water. The stock suspension may in kno~n manner also con-
tain other materials, e.g. fillers, dyes and so on.
The stock suspension flows from the stock line 4
30, in the breast box and is delivered to a vertical distributor
1055Z90
duct 5 from which the suspension passes to individual stock
suspension ducts 6 of a turbulence means 7. The stock ducts
6 contain a plurality of sections 8, 9, 10 between which
there are step-like widenings 11, 12. The downstreammost
5. duct 10 terminates just before an outlet 13 of the breast box
1, the outlet width being adjustable by means of a slide 14.
A mixing means for forming fine gas bubbles in the
stock suspension is connected to the breast box 1 and includes
a common air conduit 16 and a plurality of air ducts 15. Each
10. air duct 15 leads from the common air conduit 16 and is con-
nected to a respective upstream section 8 of the stock ducts
6 at a mixing station within the turbulence zone of the breast
box 1.
During operation, the stock suspension is fed to the
15. distributor duct 5 via the stock ~ine 4 and~flows in uniformly
distributed form therefrom through the stock ducts 6 to the
outlet gap 13 of the breast box 1 and from the box 1 onto the
wire 2. At the same time, air is fed via the air conduit 16
and is intensively mixed with the stock liquid in the duct
20. sections 8, 9 and 10 and is uniformly distributed in the form
of fine bubbles. Mixing is effected by the intensive turbu-
lence in the zone of the step-like widenings 11, 12. Inten-
sive eddies form in the flow after each widening 11, 12 and
remain in the flow even at some distance from the step in
25. question.
The conditions in the breast box 1 are so selected
that the turbulence at step 12 remains substantially undiminished
as far as the outlet 13, so that in this turbulence zone the
air bubbles are prevented from separating out of the water of
30. the stock suspension.
6.
~OS5290
As will be clear particularly from Fig. 1, the out-
let 13 is disposed at a distance A from the step-like widen-
ing 12, this distance being less than ten times the vertical
dimension D of the duct section 10. This condition approxi-
5. mately defines the critical zone where the turbulence in theflow is maintained substantially unweakened.
Referring to Fig. 3, wherein like reference charac-
ters indicate like parts as above, the stock suspension is
drawn from a chest or tank 20 having an overflow 21 and is fed
10. by a pump 22 to the feed line 4. The feed line 4 contains a
pressure controller 23 with a`throttle device 24 so that the
flow of suspension can be controlled relative to the pressure
in the line 4. The stock suspension passes from the line 4,
as already stated, to the distributor duct 5 of the breast
15. box 1. From duct 5, a return line 5' (see also Fig. 2) leads
back to the chest 20~
Referring to Fig. 3, air is fed to the air conduit
16 by a blower 25, the delivery line 26 of which contains a
: pressure controller 27 with a throttle device 28 for con-
20. trolling the air flows relative to the pressure in the line 26.
A control system as shown in Fig. 3, with which the
stock suspension and the air can be fed to the turbulence
means 7 with accurately maintained pressures, ensures that con-
stant relative proportions are maintained for the air and stock
25. suspension mixture.
It should be particularly noted that in theprocess
according to the invention and the corresponding machine, it
is possible, in some cases, to dispense with the supply of
wire water otherwise necessary in paper machines and its ad-
30. dition to the stock suspension taken from the chest 20, since
lOS5290
the stock suspension can be fed to the turbulence means 7with the same density as in the chest 20. The uniform distri-
bution of the fibers in the stock liquid, which was hitherto
obtained by adding large quantities of wire water, can be ob-
5. tained in this case by the addition of air. As a result, theenergy consumption is greatly reduced while dewatering of the
fleece on the.permeable element 2 is facilitated. Given
suitable stock suspension densities, it is even possible to
dispense with the wire otherwise required for fleece forming,
10. and to place the fleece directly on a felt, e.g. of a felt
press. The machine, e.g. a paper machine, can be greatly
simplified in this way.
Referring to Figs. 4 and 5, the breast box can
be provided with a distribution duct 5 which is followed by
15. two superposed rows of stock ducts 6 provided with step-like
widenings 11 and 12. In addition, a common air conduit 40 is
provided from which air ducts 41 lead to the individual ~ck
ducts 6. Connecting ducts 42 branch from the air ducts 41
ar,d each discharges in the region of the step-like windings 11.
20. The ducts 42 are so constructed that each two are situated in
one line and lead into the stock duct 6 at diametrically oppo-
site places.
Of course, the machine illustrated can be modified
in various ways. For example, a blower for feeding air to the
25. conduit 16 (Fig. 3) may be omitted since the suction effect of
the flow of s*ock suspension may be sufficient to draw in
the required air. Also, the turbulence means 7 may have a
different number of steps and sections than the three sections
8, 9 and 10 shown. Further, more stock ducts 6 than those
30.shown may be superposed. A different number of air ducts may
105S290
be provided to feed air to the stock ducts and, in some cases,
an annular duct may be provided which surrounds a suitable sec-
tion of the associated stock duct 6.
To satisfy the basic principle of the invention,
5. all that is required is a turbulence means which may be dis-
posed in the breast box just before the outlet.
As already stated, the wire 2 shown in Fig. 1 may
be replaced by another water permeable element, e.g. a felt.
The machine may be a double wire machine in which a fiber
10. fleece is placed between two wires or permeable elements
running together.
Finally, in the arrangement shown in Fig. 3, wire
water may be added in known manner to the]ine 5 upstream or
downstream of pump 22 for the purpose of diluting the stock
15. fed from the chest 20.
The throttle device 24 provided to control the
stock supply need not be disposed- in the stock line 4 as
shown, but may be provided in a bypass conduit extending
parallel to the pump 22. Finally, the pump 22 may be pro-
20. vided with a speed control, by means of which the stocksupply to the breast box 1 can be controlled.
25.
30.
9.
