Note: Descriptions are shown in the official language in which they were submitted.
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Description
Title
COAXIAL MILL AND FEED UNIT FOR A MILL
Background of the invention
The present invention relates to a mill and also to a feed unit
for a mill.
The present invention especially relates to a
coaxial mill in which equipping and maintenance processes can be
performed in a particularly simple and time-saving manner.
In current processes for producing granulates, mills are
regularly used in order to eliminate irregularities in particle
size distribution with regard to maximum grain size and/order to
give wet granulates a structure.
As a result, subsequent
processes can be optimized or even made possible. For example,
the grain size reduction for dry granulate is for the tabletting
process or grain size reduction for wet granulate is in order to
be able to dry this more quickly or to give this a structure for
improving the drying, flowing and/or dosing capabilities.
The mills which are known in the prior art are added as
accessory equipment to machines and apparatus (e.g. of
manufacturing and/or production engineering) for producing
granulates. Since these machines were developed and constructed
for closed loading operation, these are provided with closable
emptying and filling openings. These pieces of apparatus, on
account of the material properties and the process requirements,
are constructed and are to be operated so that explosion risks
are reduced to a minimum and their effects do not constitute a
risk for persons in the vicinity of the machine.
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US 5,405,094 features a multistage mill in which two sieve units
by means of rotationally driven agitating elements are used for
the comminution of grinding stock. The agitating elements are
driven via a shaft which is supplied with kinetic energy by
means of a belt.
US 5,863,004 features a mill in which an agitating element,
which is arranged on a sieve element, is moved by a downward
disposed drive unit in order to force grinding stock through the
sieve unit.
Common to the mills known in the prior art in this case is that
large parts of the mill have to be taken apart in the event of a
required exchange of the sieve units or in the event of an
opening up of the grinding gear for clearing blockages, which is
time consuming and therefore costly.
Sometimes, an increased
equipping time and also the process reliability of an entire
plant can be disadvantageously influenced. Sometimes, mills of
the prior art require additional consoles and sliding or
swiveling devices in order to bring the mills into working
position, to equip them (e.g. sieve change, rotor sieve tools),
to clean them and to maintain them. Moreover, in the case of
the known solutions the grinding stock (product), in the case of
a mill drive which is arranged upstream in the flow direction,
flows from the top over the drive rod which therefore impedes
the product flow on the inlet side.
Also, in the case of
solutions with a drive which is connected downstream in the flow
direction, the product outflow in the downward direction is
impeded by the angular gear and the sieve and rotor can only be
maintained or exchanged from the top (after disassembly of the
product feed pipe). The same applies to the clearing process of
a blockage of the mill and also to cleaning and inspection
processes. It is therefore an object of the present invention
to alleviate or to eliminate the aforesaid disadvantages.
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Disclosure of the invention
The previously identified object is achieved according to the
invention by means of a mill and a feed unit for a mill. The feed
unit serves for the feed of grinding stock in the direction of the
grinding gear. According to the invention, a first interface is
provided for the mounting of a rotor of a grinding gear. The rotor
forms the moved components of the grinding gear.
A second
interface is provided for the mounting of a stator of the grinding
gear which in conjunction with the rotor effects the comminution
of the grinding stock by means of a relative movement between the
rotor and the stator. Provision is furthermore made for a feed
pipe which is designed to conduct grinding stock into the grinding
gear. According to the invention, provision is made on the feed
pipe for an annular rotary bearing which enables a relative
rotation between the feed pipe and a further component of the mill.
As a result of the annular shape, the rotary bearing can be
arranged on the feed pipe in such a way that during operation the
grinding stock makes its way into the grinding gear through the
rotary bearing.
In other words, the annular rotary bearing
encompasses at least one part of a free cross section of the feed
pipe so that the grinding stock is delivered through the "eye" of
the rotary bearing and through the feed pipe. All the grinding
stock is preferably brought into the grinding gear through the
rotary bearing. In this way, the geometry of the grinding gear
can be exceptionally favorably designed in common with its
attachment and accessibility for equipping and maintenance
purposes, as a result of which the downtimes of a mill which is
designed according to the invention can be reduced.
Date Recue/Date Received 2022-02-16
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The rotary bearing can for example be designed as a rolling
bearing or as a plain bearing. In other words, rolling bodies
can roll between an inner and an outer or an upper and a lower
race of the bearing in order to enable a particularly low
friction force in the case of high pressure forces to be
transmitted. Such a rolling bearing can be designed as a roller
bearing or as a ball bearing.
The plain bearing can have
material combinations with a particularly low sliding friction
coefficient (e.g. nylon and metal), wherein the sliding friction
coefficient can be further reduced by the use of lubricants.
The rotary bearing can for example be arranged between the first
interface for the mounting of the rotor of the grinding gear and
the feed pipe.
In this way, the feed pipe can be statically
mounted and the rotor can be rotationally arranged around the
feed pipe.
Alternatively, the feed pipe can be rotationally designed on its
own and connected to the rotor of the grinding gear in a
rotation-resistant manner. In
this case, the annular rotary
bearing is arranged between the feed pipe and a fixed component
of the mill or another fixed structure (for example a feed pipe
which is arranged upstream).
In this case also, the grinding
stock is transported into the grinding gear through the rotary
bearing.
Alternatively or additionally, the rotary bearing can be
arranged between the second interface for the mounting of the
stator of the grinding gear and the feed pipe.
In this case
also, the feed pipe of the feed unit according to the invention
can execute a rotational movement in relation to the stator of
the grinding gear, whereas it is arranged on the rotor of the
grinding gear in a rotation-resistant manner.
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The second interface for the mounting of the stator of the
grinding gear can be arranged in a mechanically rotation-
resistant manner and coaxially to a stator of an electric
machine via which the grinding gear can be (for example
electrically) driven. In this way, force transmission by means
of a belt or a chain can be dispensed with, as a result of which
energetic losses and additional installation space for the force
transmission can be saved.
The first interface for the mounting of the rotor of the
grinding gear can be connected via a belt drive or a chain to a
rotor of an electric machine, the shaft of which is arranged in
the main axially parallel to the grinding gear.
As an
alternative to an electric machine, a hydraulic or pneumatic
drive method can be provided for the machine. In this way, the
actual feed unit can be designed in a particularly compact and
volume-optimized manner, whereas the electric drive can be
arranged at another position in the production area. In this
way, maintenance or exchange of the electric machine can also
gain benefit.
The feed pipe can have an axially extended passage by means of
which a fluid can be conducted to outlets which are arranged in
the region of the grinding gear. For example, the feed pipe can
be designed as a double-walled hollow wall pipe so that the
fluid can be conducted between an inner and an outer wall into
the grinding gear.
The fluid can for example comprise a gas
and/or a liquid.
In this way, cleaning of the mill which is
designed according to the invention is simplified by no
disassembly of parts of the feed unit being required for
flushing.
Alternatively or additionally, a fluid can also be introduced
between the feed pipe and the first interface for the mounting
of the rotor of the grinding gear, for which a connection can be
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arranged in a region of the feed unit which is upstream in
relation to the grinding stock flow. In this case, a fluid feed
(a hose or the like) can be connected when required or a
permanently connected hose can be supplied with pressurized
fluid. In
this way, for example the effect of grinding stock
penetrating between the feed pipe and a rotating part of the
feed unit and leading to contamination or mechanical problems
can be prevented.
Additionally or alternatively, mixing elements, dispersion
elements, loosening elements, delivery elements can be fastened
on the rotor/stator system in the feed unit in order to break up
clumps of the raw material or product bridges or to improve the
product flow (grinding stock), for example.
Fluid (e.g. a gas) can be optionally used for example in order
to support product transportation when the mill is used in a
pneumatic conveyor.
Furthermore, a fluid (e.g. an inert gas) can optionally be used
for example in order to gas the mill interior and therefore to
reduce the oxygen proportion so that the risk of an explosion
can be reduced.
Furthermore, a fluid (e.g. a liquid) can preferably be used in
order to wet the product to be ground before its feed into the
grinding gear. This can for example improve the flow capability
and/or the service life of the grinding gear.
Proposed according to a second aspect of the present invention
is a mill which for example can be designed as a process mill in
production engineering.
The mill can alternatively or
additionally be designed as a wet mill or as a wet and dry mill
for processing granulates.
In other words, the mill can be
designed for the processing of three phase components (solid,
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liquid and gas). It comprises a rotor of a grinding gear and a
stator of a grinding gear which when interacting bring about a
predetermined comminution of grinding stock.
The rotor is
arranged on the first interface and the stator is arranged on
the second interface of a feed unit, as has been described in
detail in association with the first-mentioned inventive aspect.
Accordingly, a mill according to the invention is constructed by
mounting a rotor and a stator of a grinding gear on a feed unit
according to the invention.
Naturally, additional parts (e.g.
for closing off a feed opening for grinding stock and/or for
closing off a discharge opening for grinding stock and/or other
elements (e.g. dispersion elements for breaking up clumps,
product bridges)) or delivery elements can be included.
The first interface for the mounting of the rotor of the
grinding gear can for example enable a screwed connection
between the rotor and a further component of the feed unit.
Alternatively or additionally, a bayonet connection can be
provided between the rotor and the additional component of the
feed unit.
Alternatively or additionally, a snap-in
connection/latched connection, a clamp connection or even a
thread which encompasses an opening of the feed unit can be
provided in the rotor of the grinding gear in order to enable a
reversible and yet fixed installation of the rotor on the feed
unit. The same applies to the stator of the grinding gear and
to its connection to a second component of the feed unit
according to the invention.
The rotor and the stator of the grinding gear, as
correspondingly constructed sieve elements, can be provided with
openings and/or cutting edges.
For example, its enveloping
surface can be of truncated cone design. As a result of the
installation according to the invention, the possibility
especially arises of also using the entire sieve surface of the
grinding gear, which is oriented vertically to the longitudinal
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axis of the feed pipe, for product comminution since in this
case there needs to be no provision for a drive shaft or the
like.
Brief description of the drawings.
Exemplary embodiments of the invention are described in detail
below with reference to the accompanying drawings.
In the
drawings:
Figure 1 shows a schematic side view of an exemplary
embodiment of a mill designed according to the
invention with an exemplary embodiment of a feed
unit designed according to the invention;
Figure 2 shows a schematic side view of an alternative
exemplary embodiment of a mill designed according
to the invention with an alternative exemplary
embodiment of a feed unit designed according to
the invention;
Figure 3 shows a schematic side view of an alternative
exemplary embodiment of a mill designed according
to the invention with an alternative exemplary
embodiment of a feed unit designed according to
the invention;
Figure 4 shows a schematic side view of an alternative
exemplary embodiment of a mill designed according
to the invention with an alternative exemplary
embodiment of a feed unit designed according to
the invention;
Figure 5 shows a schematic side view of an alternative
exemplary embodiment of a mill designed according
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to the invention with an alternative exemplary
embodiment of a feed unit designed according to
the invention, comprising a belt drive and a
separate electric machine for driving the mill;
Figure 6 shows a schematic side view of an alternative
exemplary embodiment of a mill designed according
to the invention with an alternative exemplary
embodiment of a feed unit designed according to
the invention; and
Figure 7
shows a detailed view illustrating possible
embodiments of the first and second interfaces
and also seals and fluid passages.
Embodiments of the invention
Figure 1 shows an exemplary embodiment of a mill 1 according to
the invention which has a feed unit 2 according to the
invention. The feed unit 2 has a first bayonet connection 3 as
a first interface for the mounting of a rotor 4 of a grinding
gear 46. The first bayonet connection 3 is arranged on a rotor
10 of an electric machine 12 which is encompassed by a stator 11
of the electric machine.
Arranged on the stator 11 of the
electric machine 12 is a second bayonet connection 5 as a second
interface for the mounting of the stator 6 of the grinding gear
46.
Seals 22, 23, which prevent ingress of grinding stock 8
into the spaces above the seals 22, 23, are arranged in the
region of the grinding gear both between the rotor 10 and the
stator 11 and between the feed pipe 7 and the rotor 10. The
grinding stock 8 makes its way via a statically arranged filling
pipe 18 into the feed pipe 7 of the feed unit 2 according to the
invention. On the inlet side, the feed pipe 7 is provided with
a flange which has an annular rolling bearing 9b between it and
the filling pipe 18. In this way, the feed pipe 7 can rotate in
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relation to the filling pipe 18.
Also on the inlet side,
provision is made for a guide 19 for the feed pipe 7 which on
the other side is fastened on the stator 11 of the electric
machine 12. The guide 19 can butt against the feed pipe 7 with
sliding capability. Providing an annular rotary bearing 9a is
arranged between the feed pipe 7 and the rotor 10 of the
electric machine 12, the guide 19 can also be fixedly connected
to the feed pipe 7 and the inlet-side annular rotary bearing 9b
can be dispensed with since now the feed pipe 7 can be of fixed
design. On
the outlet side, the mill 1 according to the
invention is provided with an outlet pipe 20 which is fixedly
connected to the stator 11 of the electric machine 12.
An
outlet opening 21 is of explosion-proof design in order to
protect men and materials if required.
Via a control unit 24
and a control line 25, the electric machine 12 can be supplied
with electric energy in line with demand.
Figure 2 shows an alternative exemplary embodiment of the mill 1
which is represented in Figure 1 so that only the essential
differences of the mill 1 shown here are detailed below. In
order to avoid blockages and an overload of the electric machine
12, a feed control in the form of an operating element 27 or 27'
is provided.
The operating element 27, as a pivotable flap
similar to a throttle valve, is arranged in the filling pipe 18
and can be motor-driven by means of a control unit 24 via a
control line 26.
The control unit 24 is also connected to the electric machine 12
by means of a control line 25 (as described above).
If the
control unit 24 detects that an energy demand of the electric
machine 12 is increasing, it can bring the operating element 27,
via the control line 26, into the position of the operating
element 27', as a result of which the quantity of inflowing
grinding stock 8 is reduced and the load of the electric machine
12 is reduced. Correspondingly, in the case of a reduced load
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state of the electric machine 12, the operating element 27' can
be brought back into the position of the operating element 27 in
order to increase the flow of grinding stock 8 again and to
adapt the grinding gear quantity processed per time unit to the
capacity of the electric machine.
Figure 3 shows an alternative exemplary embodiment for the mill
1 which is shown in Figure 2. To be seen in this case is an
alternative embodiment of the operating element 27 which as a
cell wheel or cell wheel sluice 27 is arranged inside a circular
shell structure. If the cell wheel or the cell wheel sluice 27
rotates more quickly, more grinding stock 8 is delivered from
the filling opening 18 into the feed pipe 7. The controlling
ensues in accordance with that described in association with
Figure 2.
Figure 4 shows an embodiment of the mill 1 shown in Figures 1 to
3 which is modified with regard to the grinding stock dosing
(operating element 27). The operating element 27 is designed as
a circular membrane which can hydraulically or pneumatically
effect a tapering of the free cross section of the filling pipe
18. If the fluid pressure behind the membrane 27 is reduced,
the membrane assumes the position of the membrane 27'. If the
fluid pressure behind the membrane 27' is then increased again,
the position of the membrane 27 ensues once more. The depicted
exemplary embodiment, when pulsing fluid pressures are used for
moving the membrane 27, 27', enables an additional advantage
which is described as follows. Without changing the free cross
section inside the filling pipe 18, pulsing fluid pressures can
counteract a blockage of the filling pipe 18 without actuation
by means of a control unit 24 (corresponding to Figures 2 and 3)
being necessary.
Figure 5 shows an exemplary embodiment of a mill 1 according to
=
the invention, in which the electric machine 12 is arranged in a
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radially offset manner to the axis of the feed pipe 7.
For
mechanical energy transmission, use is made of a belt drive 13
which rotationally drives the first interface 3 for the mounting
of the rotor 4 of the grinding gear 46. The stator (not shown)
of the electric machine 12 is in its turn connected in a
mechanically rotation-resistant manner to the stator 6 via the
second interface 5 for the mounting of said stator 6 of the
grinding gear 46.
Figure 6 shows a modified exemplary embodiment, based on the
exemplary embodiments of Figures 1 to 4, in which the feed pipe
7 is designed as a hollow-wall double pipe.
In this way, a
fluid passage with circular cross section, which is extended
parallel to the flow direction of the grinding stock 8, is
created between an inner and an outer wall. Connections 17 are
provided for introducing fluid into the fluid passage 14 and
also into the space between the rotor 10 of the electric machine
12 and the outer wall of the feed pipe 7.
In the last-named
space, an overpressure, which prevents an inadvertent ingress of
grinding stock 8, is therefore created. The
use of the flow
passage 14 is explained in association with the detailed view in
Figure 7 which shows in an enlargement the region A which is
highlighted by dash-dot lines.
Figure 7 shows an enlarged view of the region A, marked in
Figure 6, in which are provided the first and second interfaces
3, 5 for the mounting of the grinding gear 46 in the form of
screwed connections. At the lower end of the feed pipe 7,
provision is made for two outlets 16 for fluid 15 by means of
which the grinding gear 46 can be flushed. Also, the path of
the fluid 15 which flows between the feed pipe 7 and the rotor
10 of the electric machine 12 along the seal 22 is illustrated
by means of an arrow.
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The present invention enables a particularly compact type of
construction and consequently savings with regard to overall
height and required mechanical interfaces. As a result of this,
a considerable cost reduction of the construction, of the parts
and of maintenance/equipping of the mill according to the
invention compared with arrangements which are known in the
prior art can be achieved. A torque drive with almost constant
torque over the rotational speed can be used for driving the
grinding gear.
Moreover, the operation can be optimized by
means of a transfer of vibrations to the housing, to the sieve
insert and to the sieve rotor (grinding gear).
