CENTRIFUGAL MILL

BROYEUR CENTRIFUGE

English Abstract

ABSTRACT
A centrifugal mill comprises a cylindrical grinding
drum, which performs a rotation about its own axis and a revo-
lution in a circular orbit about a stationary axis of revo-
lution, which is parallel to the axis of the drum, at a cons-
tant speed ratio between said rotation and revolution. The
distance form the drum axis to the axis of revolution is
smaller than the radius of the grinding drum. A feeder is
provided at one end of the grinding drum. Discharge means are
provided at the other end of the grinding drum. The feeding
and discharge zones of such mill are subjected to wear and
grinding elements may be thrown out of the mill. This is
prevented in that the grinding drum is provided at each end
with a generally conical extension, a volute feeder is mounted
on the generally conical extension at the feed end, and the
generally conical extension at the discharge end is provided
with discharge openings in its peripheral wall near its
axially outer end.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows :
1. A centrifugal mill comprising a cylindrical
grinding drum, which performs a rotation about its own axis
and a revolution in a circular orbit about a stationary axis
of revolution, which is parallel to the axis of the drum, at
a constant speed ratio between said rotation and revolution,
the distance from the drum axis to the axis of revolution being
smaller than the radius of the grinding drum, further comprising
a drive mechanism for rotating the grinding drum about the
drum axis and for revolving the grinding drum in the circular
orbit, a feeder provided at one end of the grinding drum, and
discharge means provided at the other end of the grinding
drum, characterized in that the grinding drum is provided at
each end with a generally conical extension a volute feeder
is mounted on the generally conical extension at the feed
end, and the generally conical extension at the discharge
end is provided with discharge openings in its peripheral
wall near its axially outer end.
2. A centrifugal mill according to claim 1,
characterized in that the volute of the feeder is disposed in
a plane.
3. A centrifugal mill according to claim 1 or 2,
characterized in that portion of the generally conical extension
which is provided with the discharge openings is cylindrical.

4. A centrifugal mill according to claim 1 or 2,
characterized in that a collecting channel which has a directed
discharge opening is secured around that portion of the
generally conical extension which is provided with the
discharge openings.
5. A centrifugal mill according to claim 1 or 2,
characterized in that the discharge openings in the generally
conical extension consist of slots.

Description

,.; ~E4
517
The presen~ invention relates to a centrifugal and
particularly to a centrifugal mill comprising a cylindrical
grinding drum, which performs a rotation about its own axis
and a revolution in a circular orbit about a stationary axis
- of revolution, which is parallel to the axis of the drum, at
a constant speed ratio between said rotation and revolution,
the distance from the drum axis to the axis of revolution
being smaller than the radius of the grinding drum, further
comprising a drive mechanism for rotating the grinding drum
about the drum axis and for revolving the grinding drum in
the circular orbit, a feeder provided at one end of the
grinding drum, and discharge means provided at the other end
of the grinding drum.
Published German Specification 2,631,826 discloses
a centrifugal mill which is of the kind described first
hereinbefore and comprises a cylindrical grinding drum and
is charged by means of a funnel-shaped feeder through a
vertical end portion of the drum. The discharge means of
that known mill consist of an overflow pipe disposed in the
other vertical end portion of the drum. If the grinding
drum is vertically arranged, central openings for charging
the drum and for discharging from the drum are provided in
the horizontal end plates of the grinding drum. The
discharge means may include a discharge volute, which returns
coarse material into the grinding drum.
Published German Specification 2,~47,578 also
describes such centrifugal mill which has a horizontal
grinding drum which in one vertical end portion has a central
opening, in which a feeder is disposed, whereas the other
vertical end portion of the drum has a central opening, which
contains an overflow pipe.
These mills are subjected to wear in the feeding
- 1-
' .

1146517
.
and discharging zones, and grinding balls may be thrown out
of the drum.
It is an object of the invention to reduce the
wear in the feeding and discharging zones and to prevent
grinding elements from being thrown out of the drum.
This object is accomplished in accordance with
the invention in that the grinding drum is provided at each
end with a generally conical extension, a volute feeder is
mounted on the generally conical extension at the feed end,
and the generally conical extension at the discharge end is
provided with discharge openings in its peripheral wall
near its axially outer endA
The generally conical extensions may be coaxial to
the grinding drum and to the open ends thereof. Each conical
extension may consist of a plurality of sections, which are
secured one behind the other. This will facilitate the
assembling and disassembling as well as the acces~ to the
grinding drum.
The inlet opening of the volute faces preferably
upwardly. The inlet opening is preferably so dimensioned
and arranged that during the revolution of the grinding
drum in its orbit the edge of the opening remains clear from
an area which is sufficient for a stationary feeding. If the
grinding. If the grinding drum is horizontally disposed and
the opening is reactangular, the distance between the two
edges which are parallel to the axis of the grinding drum
must exceed in that case the diameter of the circular orbit.
In such an arrangement it is not required, e.g., to provide
a flexible feeder, which is connected to the opening.
Accord-ing to a preferred feature, the volute of
the feeder lies in a plane. This will result in a particularly
uniform feeding of the charge into the grinding drum.
-- 2 --

:
11~L6517
According to a preferred feature, that portion of
the generally conical extension whch is provided with the
discharge openings is cylindrical. This results is a parti-
cularly uniform discharge.
According to a preferred feature, a collecting
" channe,l which has a directed discharge opening is secured
around that portion of the generally conical extension
which is provided with the discharge openings. In that case
the discharged matter will be collected in a simple manner
and can be removed from a single point.
According to a preferred feature, the discharge
openings in the generally conical extension consist of slots.
This will also contribute to a uniform discharge.
An embodiment of the invention will be explained
in detail but in a non limitative manner with reference to
the drawings, in which
Fig. 1 is a diagrammatic longitudinal sectional
view showing a horizontally disposed grinding drum;
Fig. 2 is a transverse sectional view taken on
line A-A in Fig. 1,
Fig. 3 is a transverse sectional view taken on
line B-B in Fig. lj
Fig. 4 is a longitudinal sectional view taken on
line C-C in Fig. 5 and showing a modification, in which that
portion of the generally conical extension which is provided
with discharge openings in cylindrical.
Fig. 5 is a transverse sectional view taken on
line D-D in Fig. 4.
Conical extensions 2a and 2b are secured to the
grinding drum at its feed 1 and its discharge end 1,
- respectively. A volute feeder 3 is mounted on the extension
2a. Discharge slots 4 are provided in the extension 2b in the
-- 3 --

.
:
1146517
conical wall close to its axially outer end,.
The volute 5 is disposed in one plane in the feeder
3. In the embodiment shown in Fig. 4, that portion of the
extension 2b which is provided with discharge openings is
' cylindrical and surrounded by a collecting through 7, which
has a downwardly facing discharge opening 8.
The advant~ges afforded by the invention reside in
that the wear in the feeding and discharge zones is greatly
reduced, that a throwing, of grinding elements out of the
drum is avoided, and that a highly uniform feeding and discharge
are accomplished as well as substantial increase in throughput.
'' ' .
.. . .
-- 4 --
'.~