Note: Descriptions are shown in the official language in which they were submitted.
L3~6
APPARATUS FOR FR~CTIONATING FIBER SUSPENSIONS
.
The present invention relates to an apparatus for
fractionating aqueous fiber suspensions containing cellu-
lose fibers, more specifically a fiber fractionating appa-
ratus of the kind disclosed in the preamble to Claim 1.
In the present application and claims there is
intended a division of an aqueous suspPnsion of cellulose
fibers into two fractions, of which the fixst contains
fibers slushed up in wat~r, which are substantially above a
given size, and the second contains fibers substantially
below a given size, the boundary between the fractions not
being sharp but depending on the statistical character of
the fractionating method.
Examples of such fiber fractionation are rough
screening, fine screening and thickening. In rough screening
the first fraction mainly contains larger fiber bundles,
shives and larger particles, while the second fraction
contains fibers of different sizes as well as fines. The
reverse condition is obtained in thickening. The first
fraction contains, generally speaking, all fibers except a
portion of fines, while *he second fractïon only consists of
liquid and fines.
The object of the present invention is to provide an
apparatus for fiber fractionation in which the incomin~
fiber suspension is divided into two fractions.
Another object is to provide such fractionations as
rough screening, fine-screening-and thickening with inter-
mediate forms of fractioning of fibers in the same apparatus
by merely changing the fractionating`means.
The intended object is achieved with a fiber frac-
tion apparatus which includes an annular chamber convergin~
towards its periphery, formed by two annular elements pre-
ferably implemented as truncated cones, of which at least
one i5 a fiber fractionating means; a collection trough
arranged concentric with the chamber and at its periphery
for fibers retained by the elements, from a centrally
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arranged rotatable shaft and agitation means rotatable with
the shaft, the agitation means having vanes extending in the
collec-tion trough and situated adjacent the fiher fraction-
atin~ means, each vane having an engagement area engaging
against the fiber fractionating means with which it coacts.
The essential features further characterizing the
invention are apparent from the claimc:~and in the followiny
different embodiments of the invention are described in
conjunction with the accompanying drawing, on which
Fig. 1 is a section of an embocliment,
Fig. 2 is a cross section along the line II-II in
Fig. 1,
Fig. 3 is an embodiment of the present agitation
means, and
Figs. 4-7 illustrate contours of vanes used in the
present invention.
The fiber fractionation apparatus according to Figs.1
and 2 has two stationary fractionating means 1,2 implemented
as annular elements which are axially, laterally arranged
relative each other and have the shape of the sweep of a
truncated cone. The elements 1,2 are made in one piece and
have perforations 23 in the form of xound holes. They are
adapted such that they have the concave ~ides facing towards
each other and are each removably attached at their outer
edges to the inner edge of an annular support element S,6.
~he support elements 5,6 are axially laterally arranged and
are connected with its outer edges to a surrounding
cylindrical housing or casing 3. Together, the support
elements 5,6 and the portion of the cylindrical housing 3
between them form an annular collection trough 4, which is
open at the inner edge of the elements 5,6 towards a fiber
fractionation chamber 22 which is disposed between the fiber
fractionating means 5,6. The fiber fractionating means 1,2
are each removably attached to their respective portions of
an inner, intermediate wall consisting of two cylinclrical
parts 10,11 concentric with the c~lindrical casing, the
parts 10,11 uniting the inner edges of the fiber fractionating
means 1,2, each to the respective end wall 14,15 of the
casing 3. One cylindrical part 10 of the intermediate wall
is on its side facing away from the chamber 22 provided w:ith
an inlet 9 for fiber suspension. The o-ther cylindrical part
11 of the intermediat~ wall is provided on its side facing
towards the chamber 22 with a wall 12 sealing against the
chamber 22. There is a lead-through in the wall 12 for a
rotatable shaft 19, which is driven by a motor 18~pro~ecting
into the room formed by the cylindrical portion 11 and the
~ l0 joining wall 12.
The rotatable shaft 19 carries two a~itatiny means 20
which are rotatable with the shaft. The agitating means 20
(Fig. 1) are attached to the shaft with the aid of a sleeve
30, which is adjustable axially on the shaft 19 ana non-
rotatably connected to it with the aid of a screwed joint atthe free end of the shaft. Two pins 31 project from the
sleeve 30, a central body 32 being attached to each pin. The
central body is rotatable about and displaceable along the
pin 31 for adjusting the position of the agitating means 20.
Two arms 33, directed towards each other, depart from the
central body 32, a vane 35 being attached to each arm. Each
vane has an orientation relative the fractionating means
with which it coacts such that-it engages with an engagement
area 33 against the fiber fractionating means, substantially
in the direction of the ~eneratrix. The ~imensions of the
vane 35 in the direction of the generatrix are such that
the vane pro~ects into the collection trough 4, ana during
rotation-of the shaft 19-has swept, after ~ne-complete
revQlution, over the entire fiber fractionating means with
which it coacts.
Further to the collection trough 4, the apparatus has
three separated spaces 22,7r8. The first space is the fiber
fractionating chamber 22, which is defined by the inlet 9
and the area between the fiber fractionating means 1,2. The
chamber 2? is open towards the trough 4 which close to its
lowest point has an opening 16 wi-th an outlet 17. The
chamber 22 communicates via the openings of the fractionatin~
3~8~i
means 1,2 with two connection spaces 7,8. One space 7 is
defined b~ the cylindrical casing 3, the end wall 14, the
part 10 of the in-termediate wall, the fractionating means 1
and the support elem~nt S which forms the right-hand side
wall of the trough 4 in Fig. 1. The second collection space
8 is defined by the cylindrical casing 3, the end wall 15,
the wall 12, the part 11 of the intermediate w~ll, the
fraction~ting means 2 and the support~element 6. A common
outlet 13 is connected to the two collection spaces 7,8
but they may each be provided with an outlet.
The casing 3, as will be seen from Fig. 2, is made in
two halves, one upper and one lower half, of which the
upper is connected by means of hinges 22 or the like to the
lower half and is thus raisable.
In accordance with the invention, the conical angle
for the fractionating means 1,2 should lie within the
interval 90 - 180 and preferably have a value of between
120 and 150. It is particularly preferred that both of
the fractionating means 1,2 have the same conical angle.
According to one embodiment, there is only one
fractionating means, the other element being blank, i.e. it
lacks perforations.
The fiber fractionating means 1,2 have pexforations
23 in the form of hc>les or slots. The holes are preferably
round holes which are cylindrical or conical, the wider
part of the conical holes facing -towards a recep$ion space 7
or 8. The slots may also widen towards the reception space,
~r have parallel side walls. The size of the perforations
depend on the size of particles it is desired to pass through
the fiber fractionating means, and varies within wide limits.
For thickening, at which only a parc of the fines passes
through the openings, the perforations have a diameter, or a
least diameter if they are conical, of O.2 - 1.5 mm, and
with a perforated area, i.e. a quotient between the total
area of the perforations and the total area of the frac-
tionating means, of at least 50~. The upper limit is about
50~ for practical reasons. When USinCJ 510ts, they have a
_ ,q _
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~idth of 0.1 - O.5 mm. The open area is also in this case
at least 30%. For screening, the openings have a diameter
of 1 - 10 mm, or a width of 0.2 - 2 mm. The open area is
between 5~ and 30~.
When using the described apparatus, the fiber suspen-
s.ion is supplied through the inlet 9 and is distributed in
the inner chamber 22 defined by the fractionating means 1,~.
- The shaft 19 with the agitating means 20 rotates in this
chamber, the vanes 35 engaging with their engaging surface
36 against the fractionating means with which they coact,
and during their movement prevent fibers and agglomerates,
- retained by the fractionating means, from fastening on said
means. The heavier fraction of the incoming material, which
has not passed through the openings 23 of the fiber frac-
tionating means, is fed out to the collection trough 4, where
it leaves the apparatus through the opening 16 and outlet 17.
The finer fraction of the incoming material is caused to pass
through the openings 23 of the fractionating means 1,2 into
the collection spaces 7,8. The latter fraction leaves the
collection space 7,8 via the common outlet 13.
Fig. 3 illustrates another embodiment of the agitating
means 20 and its attachment to the shaft 19. The arms 33,
carrying the vanes 35 via attachment means 34, depart from a
central body 29. This body is thrust into a sleeve 28 which
is rigidly attached to a sleeve 27. In the same way as the
sleeve 30, the sleeve 27 is settable axially and non-rotatably
connected to the shaft 19. The central body 29 i~ locked in a
desired position with the aid of a nut 26 on the sleeve 28.
The vane 35 consists of a plastic material with a
small coefficient of friction, e.g. plastics, and is fixed to
the arm 33 via the fixing means 34 in the part closest to the
shaft 19. Since the vane is only attached at one end and due
to its plasticity, it can bear yieldingly against the fiber
fractionating means during the rotation of the agitation
means 20. The vane 35 has a dimension in the direction of the
generatrix such that it extends into the collection trough 4~
It thereby reduces or eliminates the edge effe~t resulting in
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plugging up of the perforations nearest to the trouyh. The
cross section of the vane in the direction of the generafrix
is preferably constant.
Implementations of the vane 35 in profile, i.e. in
cross section at right angle to the direction of the gene-
ratrix, are illustrated in Figs. 4 - 7. The arrow P illus-
trates the direction of movement of thle vane. The part of the
vane 35 engaging against the fiber fractionating means is
denoted by 36 and relates to the engagement area. The engage-
ment area 36 has small dimension in the direction of movementof the vane in relation to the total dimension of the vane in
the same direction, and is farthest forward on the vane. The
art of the vane facing towards the fibre suspension may have
or more discernable areas. The first area, which is connected
to the engagement area, is denoted by 37. The angle between
the area 36 and 37 is a riyht angle or preferably acute, e.g.
90 - 40. The area 37 can be flat, convex or concave. The
part of the vane facing towards the fiber suspension can have
any of the shapes illustrated in Figs. 1 - 4. What is
essential is that the vane has a shape such that it is urged
against the fiber fractionating means by the suspension it
collides with on rotation of the agitating means 20.
Behind the engagement surface 36, seen in the direc-
tion of movement of the vane, thexe is an area 38 at a
2~ distance from the fractionating means and facing towards it.
The distance between the area 38 and the iber fractionating
means is 5% - 20% of the total dimension of the vane in its
direction of rotation. The area between the area 36 and the
area 38 has small extension as seen in the direction of
rotation of the vane.
The rear side of the vane, between the area 38 and
the portion of the vane factinq towards the fiber suspension,
has also importance for the ability of the vane to keep the
fractionating means clear. This is preferably a flat area 40,
and the angle between it and the area 38 is a right angle or
obtuse angle, e.g. 90 ~ 135.
The fiber Eractionating apparatus described hereinbe-
39~
fore and illustrated in the drawing is of course onlv to beregarded as an emboAiment of the invention. Other embodi-
ments within the scope of the main claim are therefore also
conceivable. It is thus not necessary that the shaft of the
apparatus is horizontal, as illustrated in the drawing. The
shaft may also have another orientation in space, It is of
course possible to use any conical angle for the fiber
fractionating means within the scope of Claim 1, Neither is
it necessary that the conical angle of the fractionating
means is constant along the entire length of the generatrix.
On the contrary, it is sufficient that the angle between the
geometric axis of the fractionating means and an optionally
selected tangential plane to the fractionating means is
; within the preferred interval of 45 - 90 and particularly
has a value between 60 and 75, which corresponds to a
conical angle of 90 - 180 and 120 - 150, respectively.
This thus signifies that the generatrix of the fractionating
means may also consist of a completely or partially curved
line.
Finally it should be pointed out that the agitating
means may have merely one arm, on which the vane engaging
against the fiber fractionating means is attached. Turther-
more, the arm or arms may be attached directly to the shaft
19 or via a slee~e axially adjustable on the shaft. The arms
may also be adapted resiliently, so that the vanes are
urged harder against the fractionating means for increasing
the revolutionary rate of the shaft 19.
