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Патент USA US2130983

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Sept. 20, 1938.
Filed April 5, 1954
Patented Sept. 20, 1938
Willy Kohler, Neckarhausen/Ladenburg-on-the
Ne'ckar, Germany, assignor to Joseph Voegle
V A. G., Mannheim, Germany
Application April 5, 1934, Serial No. 719,177
In Germany April 10, 1933
2 Claims.
This invention relates to improvements in wet
grinding mills in which the material to be ground
passes between several smooth surfaced rolls in
the form of a paste or thick ?uid. After each
5y; grinding stage the material under treatment is
freed or liberated into a collecting space from
which it passes to the next grinding stage. Even
such repeated grinding and loosening of the material is not found to be adequate to ensure unilil'. formly ?ne grinding on the one hand and on the
other hand this method of treatment fails to
liberate undesirable volatile constituents which
impart say, a disagreeable odour to the product.
(01. 83-12)
ranged to accommodate the material under treat
ment in the various stages of the series of grind
ing operations, which are shown as carried out
by three grinding rolls b, c and g with smooth cy
lindrical surfaces. The rolls are in any usual 5“
manner held in contact under pressure and ro
tate with different surface speeds. The roll I) is
supported wholly Within the hopper a whilst the
roll 0 forms part of one side wall of the hopper
and the roll 9 forms the base of the hopper. The 10.
sloping sides of the hopper walls together with
the rolls b and 0 form the collecting chambers
for the material which, although in the form of
These second mentioned considerations apply in
15; cases such as the ?ne grinding of chocolate and
cocoa beans, so that in many such cases it is'necessary to pass the material through a separate
stirring process which ventilates the material and
enables the volatile constituents to pass off.
The object of the present invention is to enable a very high degree of uniform ?neness to be
obtained in the product from such grinding mills
and also in connection with this grinding operation at the same time to free the material of un25 desirably smelling constituents all in a single pass
a paste or thick ?uid must be considered as in
the coarse state relatively to the ?ne state of 15
the ?nished product. The coarse product is
shown at k. The ?rst stage of the grinding takes
place between the rolls 1) and c where the sur
face of one of the rolls moves at a greater speed
than the surface of the other so as to give a 20
rubbing or grinding action. After leaving the
grinding point, the surfaces of both rolls are
cleaned by passing scrapers d and e which may,
if desired be arranged so that their pressure on
the roll surface may be adjusted from outside. 25
through the machine.
The invention consists of a grinding mill having a plurality of rolls forming a succession of
grinding pairs through which the material is
30 passed in series with collecting chambers for
the material interposed between each grinding
stage and which is characterized by the provision
of stirring mechanism in the collecting chamber
between any grinding pair and the next following pair in the series.
The effect of the interposition of this stirring
mechanism is to subject the material which has
just left or been liberated from one grinding pair
to a mixing and breaking up operation which
loosens the ?ne particles and liberates any undesirable volatile constituents and at the same time
this loosening has the effect of increasing the
grinding or comminuting action at the next following grinding pair.
The invention is illustrated in the .accompanying drawing by way of illustration in a diagrammatic fashion, it being evident that the details
of the grinding and stirring mechanism form no
important feature of this invention and may be
varied in a number of ways to suit different purposes and materials under treatment. The dia-
This action loosens the material from the roll sur
faces but does not break up the smaller cakes or
clumps of material. The material 1‘ so loosened is
in a ?ner state of comminution than the material
1c in the hopper compartment in front of the
grinding pairb and 0.
It will be understood that the side walls of the
hopper a are arranged so close to the rolls 0 and 9
that none of the material can escape.
The provision of the above described loosening
means, that is scrapers d and e on the roller pairs
0 and b is known, but in accordance with this
invention a stirring device 2' is provided in the
collecting chamber for the material 1‘ which has
been loosened or scraped from the roll surfaces
by the scrapers d and e and this stirrer further
breaks up or loosens the powder or paste and
brings it to a more uniformly thick liquid con
sistency free of lumps or cakes before the mate
rial f passes to the grinding stage between the
pair of rolls 0 and g.
This active stirring operation thus ensures
that the small solid particles are relatively dis
placed and separated to open them up to the
maximum grinding action at the next following
stage. If the material, as is frequently the case,
gram shows a form of the invention in cross section.
has been squeezed into the form of ?akes or
scales these are brought by the stirrer into a
In carrying the invention into effect according
55 to the form illustrated, a single hopper a is ar-
position throughout the mass which is in the
great majority of cases either at right angles or 55
2 .
at some inclined angle to the opening between
t the rolls of the next following grinding pair,
whereas in former designs these ?akes entered
the second grinding pair more generally in a
tangential path. In this way it is possible by
means'of this invention to decrease the pressure
between the second pair of grinding rolls and in
fact this pressure does not require to be materially
greater than that between the ?rst‘pa‘ir.
10 comminution effected is nevertheless much great-v
er owing to the fact that the pressure is applied
to the ?akes more or less always in an “end on”,
' position. The power consumption of the mill is
thereby reduced.
What I claim is:
faces of the said rolls and the adjacent chamber
walls, and rotatable about an axis generally par
allel to the axes of said rolls, said stirrer having
a surface movable into proximity to said grinding
rolls to feed the material passed between the
?rst grinding pair towards the bite of the second
grinding pair.‘
' 2. A grinding mill for use in grinding generally
?uid material possessing undesirable volatile con
stituents, said mill including three grinding rolls 10
cooperating to provide ‘two grinding pairs be
tween which all of the material is passed in suc
cession, the adjacent surfaces of the rolls con
stituting the ?rst grinding pair travelling in the
same direction, an open chamber in constant 15
1. A grinding mill for use in grinding gener
communication with the atmosphere, said cham
ally ?uid material possessingLundesirable vola+ ber being disposed in proximity to the discharge
tile constituents, said mill including three grind-r ’. from the ?rst grinding pair, and being also dis- ~
ing rolls cooperating to provide two grinding posed in proximity to the intake of the second
grinding pair, and a rotary stirrer for agitating 20
20 pairs between which all of the material‘is passed
in succession, an open chamber in constant com
the material in said open chamber and for re
munication with the atmosphere, said chamber
leasing said undesirable volatile constituents
therefrom, said stirrer being disposed within said
being disposed in proximity to the discharge
from the ?rst grinding pair and being also dis
25 posed in proximity to the intake. of the second
grinding pair, a generally stationary scraper op
eratively bearing against oneof the rolls consti~
tuting the ?rst grinding pair andv arranged to
scrape material therefrom and into said open
30 chamber, said scraper being transversely spaced
from a wall ‘of said open chamber to permit the
undesirable volatile constituents of the material
in said chamber tov escape between said scraper
and said chamber wall to the atmosphere, and a
rotary stirrer separate from said scraper for agi
tating the material in ‘said open " chamber and
for releasing said undesirable volatile constituents
therefrom, said stirrer being disposed-within said
7 chamber, and transversely'spaced‘from the sur
chamber and transversely spaced from the sur
faces of the said rolls and the adjacent chamber 25
walls, and rotatable about an axis generally par
allel to the axes of said rolls, the direction of ro
tation of said stirrer beingopposite the direction
of rotation of the ?rst grinding roll, and said
stirrer having a surface movable into proximity 30
to said grinding rolls to feedrthe material passed
between the ?rst grinding pair towards the bite
of the second grinding pair, whereby the material
discharged from between the ?rst grinding pair
and entering said open chamber will be moved by 35
said stirrer towards the bite of the second grind
ing pair along a path other than the shortest
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