Note: Descriptions are shown in the official language in which they were submitted.
11164S3
The invention relates to grinding elements o~ a grind-
ing mill, especially for a production of special kinds of paper
and cardboard.
For a production of some kinds of paper and cardboard,
as e.g. imitation parchment, tracing paper, deep-drawing trunk
cardboard, etc., it is necessary during the grinding process to
ensure a perfect fibrillation of fibres and outlet homogeneity
of the compound grinding. For these purposes there are known
grinding mills, the grinding elements of which are made of a
porous basalt-lava. But their disadvantage resides in a low
service life, high costs and difficulties in obtaining suitable
raw material. Efforts to replace basalt-lava grinding elements
by relatively cheap steel grinding elements of a high service
life provide many problems. Requirement for a perfect fibrilla- -
tion of fibres causes an increase of a non-effective pumping in-
put as well as an increase of a specific power consumption.
So. e.g. for a production of an imitation parchment,
the compound is ground for 84 - 87~ SR and a specific consumption
of power for grinding reaches in a basalt-lava pulp engine 550 -
700 XWh/t, and as to disc mills and conical ones, provided withsteel grinding elements, their specific power consumption is in
the range 750 up to 950 kWh/t. Another disadvantage of hitherto
known grinding mills provided with steel milling elements re-
sides in the fact that the quality of the compound only approach-
es to technological requirements as to the homogeneity in a per-
fection of a fibre fibrillation.
The aim of the invention is to solve a design of steel
grinding elements of grinding mills for a producticn of special
kinds of paper and cardboard, which may replace basalt-lava
grinding elements and which may obviate disadvantages of the
hitherto known grinding elements.
This problem i5 solved by the invention of grinding
~6~t,~
elements of grinding mills, especially for a production of spe-
cial kinds of paper and cardboard, consisting of at least of one
fixed disc and of one rotating disc, the function surfaces of
which -let they be plane or conical -are provided with systems
of grooves, having various depth and width. The principle of
the invention resides in the fact, that on function surfaces of
the discs there are made systems of three types of ,traight
grooves ~eing graded in width and depth and mutually linking up,
of which the first widest and deepest grooves make together
with a radial l.ine against the sense of rotation of a rotating
disc an angle ~ in a range 10 up to 20, the second narrower and
flatter grooves make with a radial line against the sense of
rotation an angle ~ = 3~, the third narrowest and flattest grooves
are directed against the sense of rotation of the rotating disc
and they make together with the second narrower and flatter
grooves and angle ~ in the range 80 up to 100, the number of
the second narrower and flatter grooves is for each first and
deepest groove at least doubled, and :Eor each cm of length of
the second narrower and flatter groove there exist 1,25 up to 2
20 third narrowest and flattest grooves, the heginnings of the first
widest and deepest grooves of the fixed disc are closed and the
ends of them are open, the beginnings of the first widest and
- deepest grooves of the rotating disc are open and the ends of
them are closed, the second narrower and flatter grooves are
open at the outer circumference of the fixed disc and they are
. closed at the outer circumference of the rotating disc, the ends
of the third narrowest and flattest grooves are closed.
The principle of the invention also resides in the
fact that the widest and deepest grooves transit in their ends
into the second narrower and flatter grooves.
The principle of the invention also resides in the
fact, that the angle ~, which is made by the first widest and
deepest grooves together with the radial line, is 15, that the
angle ~, which is made by the second narrower and flatter grooves
together with the radial line, is 45, and that the angle ~,
which is made by the third narrowest and flattest grooves together
with the second narrower and flatter grooves, is 90.
The principle of the invention also resides in the
fact that the widths of the mutually corresponding grooves of
the fixed disc and of the rotating one are identicalD
The principle of the invention also resides in the
fact that the depths of the mutually corresponding grooves of
the fixed disc and of the rotating one are identical.
An intensive fibrillation of fibres having a completely
comparable character with the work of basalt-lava grinding ele-
ments is a result of the described mechanism.
The advantage of the grinding elements according to
the invention resides in the fact that they may be manufactured
by an ordinary working process and made of steels resistent
against wear and tear, what ensures their long service life and
low price.
Tests that were carried out with grinding elements
according to the invention proved, that they are completely com-
parable with basalt-lava grinding elements as to the fibrilla-
tion of cellulose, and more over their service life is longer
and the specific consumption is lower than those ones of the
basalt-lava grinding elements. So e.g. at grinding for imitation
parchment the specific power consumption was in the range 510 -
550 kWh/t.
The tests also showed that grinding elements according
to the invention will be advantageous not only for special ~ine-
ground paper as e.g~ imitation parchment, tracing paper etc.,
but they may he applied in a production of strong paper if there
is required to increase mechanical properties already at a low
11.~6~3
stage of grinding. Another application area is a finish grind-
ing of old paper, when it is required to renew the plasticity
and weave ability of fibres of a limited shortened effect.
In one aspect of the present invention there is pro-
vided grinding elements for a grinding mill, especially for the
production of special kinds of paper and cardboard, comprising
at least one fixed disc and one rotating disc, the working sur-
faces of the said discs being in a plane or of conical shape
and provided with groups of grooves of various widths and depths,
further comprising that on the working surfaces of the discs
there are provided spaced groups of three types of straight
grooves each being of varying width and depth and mutually link~
ing up, one with another, of which, respective a group, the
first widest and deepest groove is inclined against the sense of
rotation of a rotating disc, making together with a radial line
an angle ~ having a range 10 to 20, the second narrower and
flatter groove is inclined against the sense of rotation, making
together with a radial line an angle ~ = 3~, the third narrow-
est and flattest groove is also directed against the sense of
rotation of the rotating disc and makes together with the
second narrower and flatter groove an angle ~ having a range
~30 to 100, there are at least two second narrower and flatter
groove extending from each first widest and deepest groove and
for each 1 cm of length of the second narrower and flatter
groove there are spaced 1.25 to 2 third narrowest and flattest
grooves, the beginnings of the first widest and deepest grooves
of the fixed disc are closed and the ends of them are open at
the outer circumference of the disc, the beginnings of the
first widest and deepest grooves of the rotating disc are open
and the ends of them are closed adjacent the outer circumference
of the disc, the second narrower and flatter grooves are open
at the outer circumference of the fixed disc and they are
~llf~ t~
closed at the outer circumference of the rotating disc, and the
ends of the third narrowest and flattest grooves are closed on
both discs.
In order that the invention may be clearly understood
and readily carried into effect, two preferred embodiments
thereof are, by way of example, hereinafter more fully described
and illustrated in the accompanying drawings, in which:
Embodiment 1
Figure 1 shows a section of a working part of a grind-
ing mill,
Figure 2 shows a detail of a working surface of a
fixed disc,
Figure 3 shows a detail of a working surface of a
rotating disk;
Figure 6 shows a section of a fixed disc according to
Figure 2,
Figure 7 shows a section of a rotating disc according
to Figure 2,
Embodiment 2
Figure 4 shows a detail of a working surface of a
function surface of a fixed disc,
- Figure 5 shows a detail of a working surface of a
: rotating disc.
A device according to Figure 1 consists of a box 3, to
which a cover 4 with an inlet branch 5 is fixed, which is axially
situated with respect to an inner space 9 of the box 3. The box
3 is provided with an outlet branch 6, which is radially situated
with respect to the inner space 9 of the box 3. A gland 7 is
built in the wall of the box 3 coaxially with the inlet branch
5, in this gland 7 there is rotatingly seated a shaft ~, on the
conical end ~1 of which there is wedged a rotor body 21, locked
by means of a nut 12. A fixed disc 1 is fixed by means of not
-4a-
S3
drawned screws to the cover 4. ~ rotating disc 2 is fixed by
means of not drawned screws to the rotor body 21.
On the function surface of the fixed disc 1 according
to Fi~ure 2 and of the rotating disc 2 according to Figure 3,
there are made systems 31, 41, Sl, or 32, 42, 52, of three types
of straight grooves 310, 410, 510, or 320, 420, 520, which are
graded in width and depth in the direction of flow of the com-
pound. The grooves 310, 410, 510, or 320, 420, 520 mutually
link up. The first widest and deepest grooves 310 or 320 make
together with the radial line 100 or 200 against the sense of
rotation of the rotating disc 2 an acute angle ~. The second
narrower and flatter grooves 410 or 420 make an angle ~ which
is three times bigger than the angle ~. The third narrowest and
flattest grooves 510 or 520 are directed against the sense of
rotation of the rotating disc 2 and make together with the se-
cond narrower and flatter grooves 410 or 420 an angle ~.
The second narrower and -flatter grooves 410 or 420 are
at least doubled for each first widest and deepest groove 310 or
320, For each 1 cm of the length of the second narrower and
flatter grooves 410 or 420 there exist 1,25 up to 2 third narrow-
est and flattest grooves 510 or 520.
On the fixed disc 1 the first widest and deepest
grooves 310 are in their beginnings 313 closed and in their ends
314 open, the second narrower and flatter grooves 410 are in
their beginnings 413 and ends 314 open, the second narrower and
- flatter grooves 410 are in their beginnings 413 and ends 414
open, and the third narrowest and flattest grooves 510 are in
their beginnings 513 open and in their ends 514 closed.
On the rotating disc 2 the first widest and deepest
grooves 320 are in their beginnings 323 open and in their ends
closed, the second narrower and flatter grooves 420 are in their
beginnings 423 open and in their ends 424 closed, and the third
narrowest and flattest grooves 520 are in their beginnings 523
--5--
open and in their ends 524 closed.
The first widest and deepest groove 310 of the fixed
disc 1 according to Figure 4 transits in its end 314 into the
second narrower and flatter groove 410, and the first widest
and deepest groove 320 of the rotating disc 2 transits in its
end 324 into the second narrower and flatter groove 420.
Depths 312, 412, 512 of the fixed disc 1 according to
Figure 6 and depths 322, 422, 522 of the rotating disc 2 accord-
ing to Figure 7 are getting smaller continuously in the direc-
tion of the compound flow.
The function or working of the grinding elements is
as follows:
The compound comes from the inlet branch 5 into the
first widest and deepest grooves 320 of the rotating disc 2 and
it flows into the second narrower and flatter grooves 420 of the
rotating disc 2 and into the third narrowest and flattest grooves
520, In this way the whole grinding area is filled up. A free
flow of the compound and of the rotating disc 2 outside the
grinding area is limited by closed ends 324 of the first widest
and deepest grooves 320, by the closed ends 424 of the second
narrower and flatter grooves 420 and by closed ends 524 of the
third narrowest and flattest grooves 520, The compound is
forced to flow through the third narrowest and flattest grooves
510 into the second narrower and flatter grooves 410 and into
the first widest and deepest grooves 310 of the fixed disc 1,
and only then it may flow outside the grinding area. The des-
cribed cycle of flow of the compound makes sure, that in fact
all fibres are worked in the working process, and in this way a
high homogeneity of the compound grinding is ensured.
Simultaneously with a forced compound flow from the
system of the first widest and deepest grooves 320, of the se-
cond narrower and flatter grooves 52 of the rotating disc 2 into
the system of the third narrowest and flattest grooves 51, of
the second narrower and flatter grooves 41 and of the first
widest and deepest grooves 31 of the fixed disc 1, a limitation
of an uneffective pumping input comes in question what causes
a considerable decrease of a specific power consumption.
If the compound passes through the third narrowest and
flattest grooves 520 of the rotating disc 2, which are in their
ends closed, and through the third narrowest and ~lattest grooves
510 of the fixed disc 1, which are closed in their ends, then
there the grinding of the compound is relatively thickened,
what is caused by the fact, that water and fine components
easily go out, and unworked bigger fibres are caught on walls
of the third narrowest and flattest grooves 520 of the rotating
disc 2 as well as on walls of the third narrowest and flattest
grooves 510 of the fixed disc 1 and they are subjected in a
thickened condition to grinding.
Although the invention is illustrated and described
with reference to two preferred embodiments thereof, it is to
be expressly understood that it is in no way limited to the
disclosure of such preferred embodiments, but it is capable of
numerous modifications within the scope of the appended claims.
