Note: Descriptions are shown in the official language in which they were submitted.
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72883-1
The present invention relates to a method for the
automatic adjustment of the grinding gap which determines the .-
grain structure of the comminuted material in a comminutor. The
comminutor comprises a first rotating comminuting tool and at
least one additional comminuting tool allocated 'thereto which
is adjustable relative to the first comminuting tool. The said
tools form a grinding gap, which avoids substantial changes to
the grain structure of the comminuted material. The second
comminuting tool is moved at intervals towards the rotating
comminuting tool by means of a drive mechanism when the comminutor
is empty until first contact with this comminuting tool occurs.
Upon detection of the noise resulting through this contact by
means of a microphone, the movement is reversed in order to space
this comminuting tool a distance from the rotating comminuting
tool to provide the desired operation.
The present invention relates in particular to a method
of operating an impact mill or an impact breaker. These comminu°
tors consist of a rotor provided with impact members, in
particular impeller bars, and so-called impactors (counter tools)
and if necessary also grinding paths which during operation form,
with the impeller bars, a grinding gad which in addition to the
rotor speed affects the degree of comma.nution. Due to wear and
tear of the impeller bars and the impactors, this grinding gap
gradually becomes larger during operation so that the product
produced is coarser,
It is the object of the invention, however, to provide
a comminutor which produces as constant a product as possible.
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For this reason the impactors and the grinding paths are arranged
to be adjustable with respect to the rotor. The impactors are
pivotably arranged in the housing so that their distar_ce from the
rotor can be changed.
To simplify the description, reference is made here-
below and in the claims to only one impact mill.and to only one
such impact mill with only one impac;tor although impact mills and
in particular impact breakers generally have a plurality of
impactors and if necessary a grinding path, connected in series.
Adjustment of the grindincJ gap most suitable for the
respective comminuted material was previously carried out when the
impact mill was stopped, at which time the distance between the
impeller bars of the rotor and the impactor could be measured
after opening the housing. However, since it is necessary to
readjust the grinding gap at intervals as a result of the
relatively high wear occurring in the impact mills, a loss of
production occurs as a result of.frequer~t stopping the impact mill.
An attempt was therefore made to readjust the impactor during
operation, by use of a non-contact limit sensor to prevent the
impactor (which is adjustable as a function of the grain composi-
Lion of the comminuted material) from coming into contact with the
impeller bars of the rotor (German 05 20 18 496). However, this
proposal presented considerable difficulties and it thus did not
gain favour in practice:
Another proppsal for adjusting the impactor during
operation to the correct distance.from the rotor (German OS
2 034 672') involved det~rmiriing through a series of tests with
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different comminuted material the wear to which the impellers
bars and the impactor were respectively subjected during the
operating period, and thereafter continuously or gradually
placing the impactor closer to the rotor. This, however,
necessitates extensive preliminary tests, the results of which
are not sufficiently accurate due to fluctuations in the
composition of the comminuted material.
Finally, an attempt was made to adjust the distance of
the impactors from the rotor to that most suitable far the
respective comminuted material by slowly advancing the impactor
at intervals towards 'the rotor with the impact mill in each case
empty of comminuted material and upon contact of the impeller
bars of the rotor with the impactor made known by a microphone
this impactor was moved back a measurable distance corresponding
to the desired grinding gap. Such an impact mill is illustrated
in the journal "Aufbereitungstechnik" 1975, No. 8, in Figure 7
of the article "Hartzerkleinerungsmaschinen fur neue
Verfahrenstechniken" (Comminutors for new Process Technologies)
and was described in greater detail in operating instructions
published December 12, 1974 for an impact mill delivered by the
firm HAZENIAG Dr: E. Andreas GmbH & Co.
The required'cirouit arrangements (switching on the
actuating drive for the impactor, reversing movement following
signallying by a-microphone during contact, switching off the
actuating dr:i.ve following a desired long return movement of the
impactor) were carried out by hand.
Such a control system (similar tothat according to
CA 02014021 2000-02-23
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4
U.S. Patent 3,035,.782) :requires a high degree of concentration
by the operator with respect to hearing or visual impressions
and the ability to react quickly, which the operator is not
always capable of..
It is am object of the present invention to improve
this known method to eliminate these human shortcomings and to
provide automatic adjusi~ment of the impactor. This provides
for an impact mil7_ that can be operated completely
automatically by ;~witch:ing on its drive motor and starting the
feed device for tree comminuted material.
The invention provides a method for automatic
adjustment of a grinding gap determining grain structure of
comminuted material in a comminutor, said comminutor comprising
a first rotating c;omminuting tool and at least one second
comminuting tool c;ooper<~ting therewith, said second tool being
adjustable with respect to the first comminuting tool and
forming said grincting g<~p therebetween, wherein to avoid
substantial changes to t:he grain structure of the comminuted
material over time: the second comminuting tool is periodically
adjusted when the comminutor is empty, movement of the second
comminuting tool being controlled automatically by a computer
which actuates a drive mechanism for moving said second tool,
said adjustment method comprising: switching off supply of
material feed to t:he cornminutor and passing a first signal to
the computer after a de~~Lay to ensure that the comminutor is
empty; passing a second signal to the computer produced by a
microphone from general running noises of the comminutor when
empty; said computer aft:er receipt of said first and second
signals causing said second comminuting tool to advance slowly
towards said first. rotating comminuting tool; generating a
third signal that for the most part results only from hard
noises occurring urhen the advancing second comminuting tool
reaches a point of: contact with the first rotating comminuting
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tool, and passing said third signal to the computer; upon
receipt of said third signal the computer causing said second
comminuting tool to reverse from said point of contact, the
computer controlling reverse movement of the second comminuting
5 tool and terminating such reverse movement after a
predetermined distance.
The first signal ensures that the impact mill is in
actual fact free of com,minuted material and second signal
confirms that the rotor of the impact mill is actually
rotating. The modified third signal guarantees that the
reversal of movement is actually controlled by the recurring
noise produced by the impact of the impeller bars against the
impactor and not :by similar noises caused, e.g. by any stones
or other random material still falling from the material feed
into the impact mill.
The invention also provides an apparatus for
automatic adjustment in a comminutor of a grinding gap
determining grain structure, said comminutor comprising: a
first rotating co~mminuting tool; at least a second comminuting
tool which is provided with a drive unit to effect adjustment
thereof and which can be adjusted with respect to the first
rotating comminuting tool by means of the drive units; a
microphone disposed on a housing of the comminutor,
characterized by .amplifiers following the microphone a divider
transmitting an amplified signal coming from the microphone
into two channels, one of which leads to a computer via a
signal decoupler with a low trigger threshold and the other
leading to the computer via a signal decoupler with a high
trigger threshold, the computer being programmed in such a way
that after receiving a delayed signal resulting from material
feed being switched off, the computer actuates the drive unit
to cause: the se~~ond comminuting tool to approach the first
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5a
rotating comminuting tool; reverse movement of said second tool
as soon as a signal overcoming the high trigger threshold and
of specific strength and duration reaches the computer;
termination of the' reverse movement according to an input
program; and re-start o:E material feed.
This method, which is preferably to be used for
impact mills, can howevESr, also be used for other comminutors.
For example, this can thus include a roller mill comprising two
rotating rollers, one oiE which is adjustable with respect to
the other roller Y>y means of a drive mechanism. With the
roller mill empty and with a predetermined grinding gap, only
low level noise i~; audible, this noise differs sharply from the
hard noise resulting
72883--1
when the rotating rollers touch one another. Out-of-roundness
of 'the rollers or processing or wear marks on the surface of the
rollers, for example, can be responsible for this.
An advantageous embodiment of the method according to
the present invention results if the movement of 'the second
comminuting tool (impactor) towards the first comminuting tool
is immediately stopped with the accurrence of a first partial
signal resulting from a hard noise and is resumed if no
additional partial signals follow, the movement being reversed if
partial signals of a specific strength and length or a specific
minimum number of partial signals in one unit of time indicate to
the computer 'that the comminuting tools are touching one another.
The procedure according to the present invention for
adjusting the impactor of an impact mill permits completely
automatic operation of the impact mill 9.f a computer program
(software) is matched to the material to be comminuted. The
program determines at what intervals the impactor is to be
re-adjusted and'causes the material feed to be stopped beforehand
and started again afterwards.
If the comminuted material is re7.atively soft so that
wear is very slight, then it may be sufficient 'that the impactor
be adjusted in accordance with the invention at the start of
work before the comminuted material is fed in and with no
correction being necessary during the day.
It is advantageous if the computer determines by means
of the program operating it; tie distance of the impactor from
the rotor according to the desired gain structure and
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72883-1
consequently carries out the adjustment of the impactor (of the
grinding gap) automatically. ~y this means it is especially easy
to change the grain structure of the comminuted material.
It is also possible to program the computer in such a
way that after the input of new values for the distance of the
comminuting tools from one another (the grinding gap) or other
data relating to the comminuted material, re-adjustment may be
carried out by use of the present invention.
To simplify the apparatus for carrying out the method,
signals b) and c) are, according to a further embodiment of the
present invention, derived from a common microphone with the
signal coming from the microphone distributed to two channels
following amplification.
It is advantageous if with each adjustment of the
grinding gap, the compwter stores the distance covered by the
adjustable comminuting tool, the impactor, compares it with pre-
programmed values and with help of the input program indicates
the rate or the state of wear, the remaining 'working time or the
necessity of changing the comminuting tools, the amount of
comminuted material produced per set of comminuting tools and
similar data to the operator or a superordinate computer.
Completely automatic operation of the comminutor is thus possible~
this operation being interrupted only to change the worn
comminuting tools by hand or possibly to carry out other repair
work.
If tha material to be comminuted by the impact mild
consists o~ matexial in which there may also be uncomminutable
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72883-1
constituents, the device may include an elastic intermediate
member in known fashion (German OS 35 25 101, EP 0 019 541) in
the rods or the like transmitting the adjusting drive. This
intermediate member allows the impactor to remain at a distance
from the rotor at all times if such a constituent gets between
the rotor and the impactor. However, in a fully automatic
operation other dangers can arise with such a design. Pieces of
the comminuted material may, for example, jam between the
impactor and the side walls of the housing and through this stop
the impactor. If, in such a case, the drive mechanism of the
impactor is started so as to approach the rotor, then the
elastic intermediate member is placed under tension by the drive
mechanism. If, for example, the blockage is loosened as a result
of vibrations occurring during comminution work, the impactor is
brought into contact with the rotor by the action of the stressed
intermediate member in such a way that it can impact against the
impeller bars and can cause considerable domage to the impact
mill.
To prevent this, the present.invention provides for an
additional intervention in the method cha~a.cterized above in that
the drive mechanism of the impactor'is stopped during movement
towards the rotor if the'elastic intermediate member is
compressed from the direction of the drive mechanism. In this
situation, the impactor can be moved back and forth once or
several times by means of the computer program or by manual
control. following a warning signal, until re-adjustment of the
impactor to the :rotor can oceux after the blockage :is loosened.
_ g _
7zss3-1
If the actuating drive of the impactor occurs by means
of an electric motor, the elastic intermediate member is best
formed by a spring and the means for triggering the warning
signal is formed by a control element whose switching state
changes if, as described above, the spring is compressed from
the direction of the drive mechanism.
However, the elastic intermediate member can also be
formed in known fashion (German OS 35 25 101) by a pneumatic
spring, whereby the warning signal is then triggered by the
increase in presssure occurring during compression of the air
cushion from the direction of the drive mechanism. Use of a
pressure gauge in a similar connection is known from German OS
35 25 101, Figure 2, part 21, though in contrast to its present
use, it serves to maintain the pressure of the elastic inter-
mediate member,
To carry out the method described at the beginning for
operating a comminutor whose second comminuting tool can be
adjusted to the desired distance from the first rotating
comminuting tool by means of a drive unit with the aid of a
microphone provided on the housing of the comminutor, a device
is used according to the present invention which amplifies the
signal coming from the microphone and then distributes it to two
channels, the signal of the ane channel being fed via a signal
decoupler with a low trigger threshold and the signal of the
other channel fed via a signal decoupler with a high trigger
threshold to a computer programmed in such a way that ° provided
the signal overcoming the lowtrigger threshold reaches it -
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72883-1
after receiving a delayed signal resulting from the material feed
of the comminutor being switched off, it switches on the drive
unit of the adjustable comminuting tool so that this comminuting
tool approaches the first rotating comminuting tool, reverses
this movement as soon as a signal overcoming the high trigger
threshold and of a specific strength and duration reaches it,
stops the return movement according to an input program and
starts the material feed again.
To carry out the method described at the beginning for
ZO operating an impact mill whose impactor can be adjusted to the
desired distance from the rotor by means of a drive unit with the
aid of a microphone provided on the housing of the impact mill, a
device is used according to the present invention which amplifies
the signal coming from the microphone and then distributes it to
two channels, the signal of the one channel being fed via a signal
decoupler with a low trigger threshold and the signal of the other
channel fed via a signal decoupler with a high trigger threshold
to a computer progran~ned in such a way that - provided the signal
overcoming the low trigger threshold reaches it ° after receiving
20 a delayed signal resulting from the material feed of the impact
mill being switched off, it switches on the drive unit of the
impactor so that this impactor approaches the rotor, reverses
this movement as soon as a signal overcoming the high trigger
threshold and iri multiple sequence reaches ivt, stops the return
movement according to an input program and starts the material
feed again.
To proeess the signals after avercoming the trigger
thresholds for improved pick-~up in the'computer, the signal
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decouplers representing the trigger thresholds are followed by
subsequently triggerable time-switches which convert the
frequency signals into high signals and, starting at a minimum
frequency, transmit a constant high signal to the computer.
To safeguard the impactor in case of blockage'in the
housing of the impact mill, a control element is provided on the
part transmitting the drive of the impactor to this part and on
the part connected thereto via an elastic intermediate member,
the switching state of this control element changing during
compression of the intermediate member from the side o~ the drive
mechanism and generating a signal by means of which the drive of
the impactor is stopped or changed via the computer, for example
in such a way that the impactor is moved back and forth over a
short distance several times until the blockage is loosened and
the change in the switching state of the control element no
longer exists.
The present invention is illustrated in the drawings
which show in
Figure l: an impact mill in vertical section with the
apparatus required for automatic operatipn according to the
invention,
Figure 2.: a flow diagram of the devices provided for
adjustment of the impactor, and
Figure 3: a suspension of an impactor with an elastic
intermediate member,-on an enlarged scale.
The impact mill illustrated in Figure 1 comprises a
housing 1 in which a rotor 2 is rotatably disposed about a
~0140~~_
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72883-1
horizontal axle 3. The rotor 2 is provided with four impeller
bars 4. An impactor 5 is swivel-mounted about an axle 6 in the
housing 1 above the rotor 2. The i;mpactor 5 is equipped with
wear plates 7 on the side facing the rotor. The bottommost
wear plate 7a in conjuction with an imaginary cylindrical
surface 8 described by the outer edges of the impeller bars ~
during rotation form a grinding gap 9 the width of which varies
depending on the swivel position of the impactor 5. The impactor
is swivelled, as is also shown in Figure 3, by means of an
electric motor 10, a worm gearing 11, a spindle 12, an elastic
intermediate member 13 and an additional connecting link 14
which is hinged to the impactor 5. A control element 15 is
provided on the spindle 12 and a switching lug l6 is provided on
the intermediate member 13. The switching state of the control
element l5 is changed with the aid of the switching lug if the
elastic intermediate member 13 is compressed from the direction
of the drive mechanism. This can happen if the impactor 5
cannot move forward in the direction of the rotor, fox example
because of blockage in the housing 1 of the impact mill.
However, such a change in the switching state has no effect if
the elastic intermediate, member is compressed'fxom the direction
of the rotor, for example because a constituent that cannot be
comminuted is be ween the rotor 2 and the impac~tor 5 and forced
the latter away from the rotor.
A pulse counter comprising a toothed disk 17 and an
approximation s~ritch 28 is also provided in the drive mechanism
10, 11, 12 of the impactor 5. This pulse counter measures the
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72883-1
movement of the impactor 5 and evaluates it for the adjustment
process.
A microphone 18, which converts the noise of the impact
mill into electric signals, is provided on the housing 1.
As Figure 2 shows, the signals from the microphone 18
pass through a preamplifier 19 and an amplifier 20. The signals
are then conducted through two channels 21, 22 which lead to two
signal decouplers 23, 24 with differently set trigger thresholds.
The signal decoupler 23 has a relatively low threshold which
20 passes the noise resulting when the impact mill is empty. The
corresponding signal is processed in a subsequently triggerable
time-switch 25 into a longer lasting high. signal which reaches
the computer 27. The signal decoupler 24 has a high threshold
and therefore only passes hard signals such as those resulting,
for example, from the impact of the impeller bars 4 against the
impactor 5. These signals are then coupled to the computer 27
as high signals via a subsequently triggerable time-switch 26.
The subsequently triggerable time-switch 26 is set in such a way
that starting from a specific number of pulses or impacts, for
20 example 7/second,:a constant high signal occurs at the output
which is fed to the cor~iputer.
The computer is: also influenced by.the inductive
proximity, switch 28 Which; is controlled by the position of 'the
impactor. This signalforms the basis for calculating the
adjustment of the impactor relative to the xotor 2 via a geared
motor l0. This adjustment is controlled by the computer by, means
of a program (software) , not ill.ustrated', which is adapted' to
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provide for the comminuter requirements. The computer also
switches off and on 'the feed device for the material to be
comminuted according to the program, so that acknowledgement of
the disconnection is delayed by a switch cabinet 29 provided with
contactors. Additional interventions in the operating method of
the computer 27 can be carried out by hand through the members
provided in the switch cabinet 29, provided such functions are
not already carried out by means of the computer program. The
control element 15, which is designed as a proximity switch, is
also connected to 'the computer 27. This control element ensuring
that the impactor 5 can also be adjusted.
The device according to the present invention operates
as follows.
If the impactor 5 of the impact mill is to be moved .
closer to the rotor 2 because the grinding gap has become too
large due to wear of the impeller bars 4 and the wearing plates 7
of the impactor (that is, it is to be moved to a distance that
corresponds to a narrower grinding gap), then with the rotor
running the material feed is stopped either by hand or automatic-
ally thus allowing the impact mill to empty. This is a pre-
requisite in order for the components dependent on the signals
of the microphone 18 to work correctly. The microphone then only
picks up the no-load noises of the impact mill. This signal is
passed to the amplifiers 19, 20 and the channel 21 and hence to
the low trigger threshold of the signal decoupler 23. The
signal ~thereaftex reaches -the subsequently triggerable dime-switch
from which it is p cked up by the computer 27 as a high
signal. If, in addition, a delay signal reaches the computer
20~.~~1~.
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72883-1
from the switch cabinet 29, demonstrating 'that the material feed
is in fact switched off - it would be possible that even with
the material feed running no material is temporarily fed into
the impact mill because, for whatever reason, no material is
reaching the feed - this guarantees that adjustment of the
impactor can be carried out without interference from the
material.
The signals applied -to the signal decoupler 24 from the
microphone 18 via the amplifiers 19, 20 and the channel 22 (this
involves the same signals reaching the signal decoupler 23) are
first of all absorbed by this decoupler because of its high
threshold. It is, however, possible that scattered signals
resulting, for example, from material subsequently falling into
the impact mill, overcome the threshold and reach the
subsequently triggerable time-switch 26. These are individual
signals or those in erratic sequence from which the subsequently
triggerable time-switch cannot generate a constant high signal.
The following adjustment process of the impactor 5
consists of two phases. zn the first phase the impactor is
slowly brought closer vto the rotor 2 by the electric motor 10.
If it comes so close to the rotor that the impeller bars 4 hit
against the foremost wearing plate 7a' of the impactor, then hard
impact noises result at regular intervals (four strikes per
rotation of the rotor). These noises are picked up by the micro-
phone 18 and are transmitted as strong signals capable of
exceeding the thresho7:d of the signal decoupler 24 and hence
reach the computer 27 as corresponding high signals. The
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72883-1
subsequently triggerable time-switch 26 thereby ensures that the
computer only reacts to these signals if a specific minimum
number of these impact noise signals occur per unit of 'time and
thus clearly establishes that they :result from the impact of the
impeller bars against the impactor and are not noises from other
sources. To this end, the subsequently triggerable time-switch
transmits a con scant high signal to the computer. The computer
then stops the movement of the impactor and reverses such move-
ment. The return movement occurs until the gap width 9 between
the rotor 2 and the impactor 5, which is determined by the
computer program, is reached.
The computer can determine the number of rotations of
a gear member required to move the impactor towards the rotor 2,
4, for example by means of a pulse counter 17, 28 moumted in the
actuating drive 10 of the impactor 5, and then - starting from
this number as the zero position of the impactor - can turn back
the gear mechanism by the number of rotations that corresponds
to the desired new distance of the impact~or from the rotor, that
is corresponds to the desired gap width 9. By means of the
empirical values determined during practical. operation and that
can be-incorporated into the respective program (software), re-
adjustment'of the impactor can occur automatically in that the
adjustment process is fromtime to time carried out automatically
at specific intervals and to the necessary extent.
