Title of Invention

METHOD AND DEVICE FOR CONTROLLING A CRUSHER, AND A POINTER INSTRUMENT FOR INDICATION OF LOAD ON A CRUSHER

Abstract A crusher has a first crushing means (4) and a second crashing means (5) together with the first crushing means (4) defining a crushing gap (6). A measuring device (12, 13) is arranged to measure the instantaneous load on the crusher during at least one period of time to obtain a number of measured values. A calculation device (11) is arranged to calculate a representative value that is representative of the highest, measured instantaneous load during each such period of time, A control device (11) is arranged to compare the representative value with a. desired value and to control the load on the crusher depending on said comparison. In this type of control; a more efficient crushing and reduced risk of the crusher breaking down are obtained.
Full Text

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Technical Field of the Invent ion
The present invention relates to a method for controlling a cnisher at which
material to be crushed is inserted into a gap between a first crushing means and a second
crushing means.
The present invention also relates to a pointer instrument for indication of the
load on a crusher, which is of the kind mentioned above.
The present invention also relates to a control system for control of the load
on a crusher. which is of the kind mentioned above.
Technical Background
A crusher of the above-mentioned type may be utilized in order to crush hard
material, such as pieces of rock material. It is desirable to be able to crush a large quantity
of material in the crusher without risking that the crusher is exposed to such mechanical
loads thai the frequency of breakdowns increases.
WO 87/05828 discioses a method to decrease the risk: of increased
mechanical load and breakdowns resulting therefrom. The number of pressure surges
above a certain predetermined level that arise in the hydraulic fluid that controls the
position of the crushing head are counted. If the count of pressure surges exceeds a
predetermined amount, the relative position of the crushing shells is changed so that the
width of the crushing gap increases. Preferably, the number of times thai the gap is
increased during a predetermined time is also counted after which alarm is given if said
number of times exceeds a predetermined amount.
The method disclosed in WO 87/05828 may to a certain extern reducing the
risk of the crusher breaking down prematurely, but does not increase the efficiency of the
crusher as regards the amount of crashed material per unit of time
Summary of the Invention
An object of the present invention is to provide a method for controtting a
crusher, which method increases the efficiency of the crusher in respect of accomplished

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crushing work, which, for instance, may result in increased size reduction of a certain
quantity of material or increased quantity of crushed material, in relation to the prior art
technique. This object is attained by a method for controlling a crusher, which is of the
kind mentioned above, which method is characterized by the following steps:
a) that the instantaneous load on the crusher is measured during at least one
period of time to obtain a number of measured values,
b) that a representative value, which is representative of the highest measured
instantaneous load during each such period of time, is calculated, and
c) that the representative value is compared to a desired value and that the
load on the crusher is controlled depending on said comparison.
An advantage of this method is that the control is based on a value that is
representative of the highest instantaneous loads, also called the load peaks, on the crusher,
i.e., the loads that involve highest risk of mechanical damage on the crusher. Thanks to
this, an operator can be sure that the function of the crusher is not risked, irrespective of
how the crusher is supplied with material. The operator can, by ensuring that the supply of
material to the crusher becomes even as regards, among other things, quantity of material,
moisture content, size distribution and hardness, decrease the highest instantaneous loads-
Thereby, the crusher can operate at a high average load without increasing the risk of
breakdown, In crushes that have an even supply and a material which does not cause high
load peaks, the method according to the invention will mean that the crusher operates at a
higher average load which means a higher efficiency, than what previously has been
possible. In crushes that have an uneven supply, the method according to the invention will
enable incentive to alter the supply so that it becomes more even with the purpose of
providing a more efficient crushing. The control of desired value is normally a stable and
safe type of control. Thus, the desired value is suitably selected to be the highest load that
tthe crusher can operate at without increased risk of mechanical breakdown. Thus, the
crusher can be utilized optimally without increasing the risk of breakdown in cases of
uneven supply or unusually hard material. The desired value can be locked fay the one
delivering the crusher, wherein the operator, which cannot affect the desired value, may
make alterations in the supply of material with the purpose of increasing the efficiency of
the crusher without, because of this, risking mechanical damage. In certain cases, it may,
however, be appropriate to let the operator increase the desired value and consciously
accept a calculated increase of the number of mechanical breakdowns in order to increase

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the efficiency of the crusher farther, Also, other ways of choosing and/or controlling the
desired value are possible.
According to a preferred embodiment, step a) also comprises that a sequence of
data is formed, which data consist of determinations of the highest load on the crusher ia
each one of said periods of time, which consist of a plurality of consecutive periods of
time. The formation of a sequence of data, where each data is the highest load during a
period of time included in the sequence, gives a control that in an advantageous way
represents the highest loads. The division into periods of time makes, among other things,
that occasional very high load peaks get a limited influence on said representative value.
According to an even more preferred embodiment, said representative value is calculated
in step b) as a mean value of data included in said sequence, A mean value gives a relevant
picture of the load peaks for the control.
Preferably, said periods of time follow immediately upon each other. An
advantage of this is that also fast courses of events are recorded quickly and may be
handled by the control, for instance a rapidly and heavily increasing load may quickly be
compensated for, the risk of mechanical damage decreasing.
Suitably, measured values are used continuously during operation of the crusher for
forming a plurality of sequences of data. An advantage of this is that the control may be
based on an almost continuous inflow of sequences and representative values calculated
therefrom. The control may thereby quickly react on alterations in the operation of the
crusher. Even more preferred is that upon calculation of said representative value of a
current sequence, at least one data ia utilized concerning highest load that already has been
utilized in an immediately preceding sequence. In this way, the sequences will overlap
each other. An advantage of this is that said representative value will be calculated several
times per unit of time. This means that the control more often receives new input data and
makes that the control better can monitor the actual course in the: crusher.
Preferably, all sequences include the same number of data concerning highest load.
Preferably, said data amounts to at least five for each sequence. At least five data for each
sequence makes that occasional very high or very low load peaks get a limited influence
on said value, a desired damping of the control being provided.
According to a preferred embodiment, at Least the highest and/or the lowest of the
data included in the sequence concerning, highest load is excluded upon calculation of said

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representative value of the same sequence. In this way, it is avoided that occasional very
high and/or low values, which, for instance, may depend on erroneous measurements or
occasional hard objects, gel an undesired large influence on the representative value that
then is calculated for the current sequence.
According to an even more preferred embodiment, at feast the highest as well as at
least the two lowest values of the data included in the sequence concerning highest load
are excluded upon calculation of said value of the same sequence, mone of the lowest than
of the highest values being excluded. An advantage of this is that it is avoided that the
control system "is fooled" to increase the load by virtue of a sequence randomly happening
to contain a plurality of periods of time with relatively low highest loads, If these periods
of time with low highest loads suddenly are followed by a very high highest load al the
same time as the control system already ordered increase of the load, there is a risk of
mechanical damage Thanks to the fact that more of the lowest values in the sequence are
excluded, the highest peaks get a greater Impact and the system becomes more sensitive to
the high peaks and can easier avoid that the load rises much above the desired value, A
consequence of this becomes that the desired value can be raised somewhat, with an
increased crushing capacity as a consequence, without increased risk of mechanical
breakdowns.
According to a preferred embodiment, the width of the gap is adjustable by means
of a hydraulic adjusting device, in step a) the load being measured as a hydraulic fluid
pressure in said device. The hydraulic fluid pressure frequently gives a very quick and
relevnt indication of the condition in the crusher. Thus, the risk impossible delays or faull
indications causing mechanical breakdowns decreases.
According to another preferred embodiment, in step a) the load is measured as the
power of the crusher driving device. The power of the driving device frequently gives a
quick and relevant feedback of the load on the crusher. Control based on the power of the
driving device is particularly suitable when the capacity of the driving device is what
limits the feasible load on the crusher and also at cases when the adjusting devise is not of
a hydraulic type. The power of the driving device may, for instance, be measured directly
as an electric power, if the driving device is an electric motor, be calculated from a
hydraulic pressure, if the driving device is a hydraulic motor, or, if the driving device is a
diesel engine, from a developed engine power.

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According to an additional preferred embodiment, in step a) the load is measured
as a mechanical stress on the crustier. An advantage of the is that it is possible to choose
the component that is the most critical one for the mechanical strength of the crusher and
measure a stress, such as a tension or a strain, which is representative of the stress on the
same component Thereby, a direct control of the load in relation to the load that the
crusher withstands mechanically is obtained. It is, as mentioned above, not necessary to
measure on the very critical component. On the contrary, it may frequently be appropriate
to measure a mechanical stress in a place, the stress of which correlates well against the
stress on the most critical component. Another advantage is that the mechanical stress may
be utilized as a measure of load also in cases when the adjusting device is not hydraulic
and in cases when the driving device is not limiting for the load that the crusher with-
stands.
In a crusher where it is possible to measure the load both as hydraulic fluid
pressure, as power developed by the crusher driving device and as a mechanical stress, or
at least as two of said parameters, the method may be formed with control on the load
parameter of these which currently is highest in relation to the desired value thereof. Thus,
during a period the load on the crusher may be controlled depending on measured, highest
hydraulic pressures, while during another period it may be controlled depending on
measured highest powers. In this way, the crusher can always operate efficiently without
risking damage on that component, for instance the hydraulic system, driving device or
crusher frame, which currently is exposed to the highest load relatively seen.
According to a preferred embodiment, in step c) the load is controlled by the fact
that at least some of the following steps is carried out; that the width of the gap is changed,
that the supply of material to the gap is changed, that the rotational speed of the crusher
driving device is adjusted, and that the mutual movements of the crushing means are
adjusted. Thus, the control of the load may late place in various ways and the method
being selected may be adapted to the current operational situation and the load being
controlled on. An alteration of the width of the gap, frequently gives a very quick
alteration of the load on the crusher. In cases when, for instance, it is desired to keep the
width constant, it may instead be of interest to alter the supply of material to the gap. If the
driving device is exposed to a very high load, it may be suitable to alter the number of
revolutions, It is also possible to combine a plurality of alterations and, for instance, to
alter the width of the gap and adjust the mutual movement of the crushing means
simultaneously. The latter may for instance be an adjustment of how much the crushing

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means move to-and-fro towards each other during the crushing. One example is
adjustment of the horizontal stroke of the shaft in a gyratory crusher.
An additional object of the present invention is to provide a pointer instrument for
indication of load on a gyratory crusher, which instruments makes it easier to improve the
efficiency of the crusher in respect of accomplished crushing work, which, for instance,
may result in an increased size reduction of a certain quantity of material or an increased
quantity of crushed material, in relation to prior art technique.
This object is attained by a pointer instrument, which is of the kind mentioned
above and is characterized in that the pointer instrument has
a first painter, which shows a comparative value, end
a second printer, which shows a representative value, which has been determined
after the instantaneous load on the crusher in one step a) has been, measured during at least
one period of time to obtain a number of measured vaiues, said representative value in a
step b) having been calculated as being representative of the highest measured
instantaneous load during each such period of time, said comparative value being
determined depending on the load on the crusher such that a comparison of the position of
the first pointer and the position of the second pointer gives an indication as to whether the
operation of the crusher is effective.
An advantage of this pointer instrument is that it becomes very dear to an operator
that operates the crusher if the operation is efficient or not If the first pointer shows almost
equally high a pressure as the second pointer, which shows the representative value that is
representative of the highest loads, it means that the operation of the crusher is efficient. If,
on the other hand, the first pointer shows a considerably lower load than the second
pointer, the operator gets an indication that, for instance, the supply of material to the
crusher does not work satisfactory but needs be attended to. Thus, the operator gets an
easily comprehensible indication of disturbances in the process. The pointer instrument
also gives a clear and quick feedback on measures carried out in order to get the crusher to
operate more efficiently, for instance measures in order to alter the moisture content or size
disaribution of the supplied material or to provide a more even inflow of material. The
second pointer also gives a feedback on that the control system is working and that the
load does not exceed permitted levels, which could cause mechanical breakdowns.

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According to a preferred embodiment, the first and the second pointer form sides of
a sector, the extension of which indicates the operation conditions of the crusher. The
sector, which suitably has another color than the dial of the pointer instrument, gives a
very clear visual indication of the difference between the value shown by the first pointer
and the representative value representing the highest loads. For the operator, it becomes a
ciear goal to keep the sector as small as possible since this means an efficiently operating
crusher.
According to a preferred embodiment, the first pointer shows a comparative value
that represents the average load on the crusher. The average load is a good measure of the
crushing work that the crusher performs. If the average load is close to the representative
value, which is representative of the highest loads, it is a clear indication of the crushing
operation being efficient.
According to another preferred embodiment, the first pointer shows a comparative
value, which has been determined after the instantaneous load on the crusher in a first step
having been measured during at least one period of time to obtain a number of measured
values, said comparative value in a second step having been calculated as being
representative of the lowest measured instantaneous load during each period of time. The
lowest measured instantaneous loads give, together with the highest measured
instantaneous loads, which are shown by the second pointer, a good picture of how much
the load in the crusher varies, "beating" up and down, and give indication if something
should be altered in order to decrease the variation. As has been mentioned above, the
highest loads are most serious as regards mechanical damage. However, it is also relevant
to consider to the lowest loads, since a large difference between the highest and the lowest
Joads means substantial load shifts on the crusher, which increase the risk of mechanical
damage.
An additional object of the present invention is to provide a control system for
control of the load in a crusher, which control system improves the efficiency of the
crusher in respect of accomplished crushing work, which, for instance, may result in
increased size reduction of a certain quantity of material or increased quantity of crushed
material, in relation to the prior art technique.
This object is attained by a control system, which is of the kind mentioned above
and is characterized in that it comprises

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a measuring device, which is arranged to measure the instantaneous load on the
crusher during at least one period of time to obtain a number of measured values,
a calculation device, which is arrange to calculate a representative value, which is
representative of the highest measured instantaneous load during each such period of time,
and
a control device, which is arranged to compare said representative value with a
desired value and to control the load on the crusher depending on the same comparison.
An advantage of said control system is that it increases the load at which a crusher
can operate without increasing the risk of breakdown.
Additional advantages and features of the invention are evident from the
description below and the appended claims.
Brief Descriotion of the Drawings
The invention will henceforth be described by means of embodiment examples and
with reference to the appended drawings.
Fig, \ schematically shows a gyratory crusher having associated driving, adjusting
and control devices.
Fig. 2 shows a ilow table for control of a crusher.
Fig, 3 schematically shows a first embodiment of sequences of measurements of
highest hydraulic fluid pressures during consecutive periods of time.
Fig. 4 schematically shows a second embodiment of a sequence of measurements
of highest hydraulic fluid pressures during consecutive periods of time.
Fig. 5 shows a typical geometry of a hydraulic fluid pressure curve in an efficiently
operating crusher.
Fig. 6 shows a typical geometry of a hydraulic fluid pressure curve in a crusher,
which does not operate efficiently.

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Fig. 7 shows a first embodiment of a pointer instrument, which visually shows how
efficiently the operation of the crusher is.
Fig, 8a shows a second embodiment of a pointer instrument, which shows the
operation in an efficiently operating crusher
Fig. 8b shows a pointer instrument which is of the same type as the one shown in
Fig, 8a, but which shows the operation in an inefficiently operating crusher.
Fig. 9 shows a gyratory crusher having mechanical adjusting of the width of the
gap.
Fig. 10 shows a jaw crusher and associated driving, adjusting and controlling
devices.
Descriotion of Preferred Embodiments
in Fig 1, a gyratory crusher is shown schematically, which has a shaft 1, At the
lower end 2 thereof, the shaft 1 is eccentrically mounted. At the upper end thereof, the
shaft 1 carries a crushing head 3. A first crushing means in the form of a first, inner
crushing shell 4 is mounted on the outside of the crushing head 3, in a machine frame 16, a
second crushing means in the form of a second, outer, crushing shell S has been mounted
in such a way that it surrounds the inner crushing shell 4, Between the inner crushing shell
4 and the outer crushing shell 5, a crushing gap 6 is formed, which in axial section, as is
shown in Fig. 1, has a decreasing width in the direction downwards. The shaft 1, and
thereby the crushing head 3 and the inner crushing shell 4, is vertically movable by means
of a hydraulic adjusting device, which comprises a tank 7 for hydraulic fluid, a hydraulic
pump 8, a gas-filled container 9 and a hydraulic piston 15. Furthermore, a motor 10 is
connected to the crusher, which motor during operation is arranged to bring the shaft 1,
and thereby the crushing head 3, to execute a gyratory movement, i.e., a movement during
which the two crushing shells 4,5 approach each other along a rotary generatrix and
distance from each other at a diametrically opposite generatrix.
In operation, the crusher is controlled by a control device 11, which via an input 12'
receives input signals from a transducer 12 arranged at the motor 10, which transducer
measures the load on the motor, via an input 13' receives input signals from a pressure

11
transducer 13, which measure the pressure in the hydraulic fluid in the adjusting device 7,
8,9, 15 and via an input 14' receives signals from a fevef transducer 14, which measures
the position of the shaft 1 in the vertical direction in relation to the machine frame 16, The
control device 11 comprises, among other things, a data processor and controls, on the
basis of received input signals, among other things, the hydraulic fluid pressure in the
adjusting device.
When the crusher is to be started, a calibration is first carried out without
feeding of material. The motor 10 is started and brings the crushing head 3 to execute a
gyratory pendulum movement. Then, the pump 8 increases the hydraulic fluid pressure so
that the shaft 1, and thereby the inner shell 4, is raised until the inner crushing shell 4
comes to abutment against the outer crushing shell 5. When the inner shell 4 contacts the
outer shell 5, a pressure increase arises in the hydraulic fluid, which is recorded by the
pressure transducer 13, The inner shell 4 is lowered somewhat in order to avoid that it
"sticks" against the outer shell 5, and then the motor 10 is stopped and a so called A
measure, which is the vertical distance from a fixed point on the shaft 1 to a fixed point on
the machine frame 16. is measured manually and fed into the control device 11 to
represent the corresponding signal from the level transducer 14. Next, the motor 10 is
restarted and the pump 8 then pumps hydraulic fluid to the tank 7 until the shaft 1 reaches
the lowermost position thereof. The corresponding signal from the level transducer 14 for
said lower position is then read by the control device 11, Knowing the gap angle between
the inner crushing shell 4 and the outer crushing shell 5, the width of the gap 6 may be
calculated at any position of the shaft 1 as measured by the level transducer 14. Usually,
the width of the gap 6 is calculated in the position when the gap 6 is as most narrow, i.e.
in the position where the inner shell 4 gets in contact with the outer shell 5 during the
above-mentioned calibration. However, it is also possible to calculate the width at another
position in the gap 6 in stead.
When the calibration is finished, a suitable width of the gap 6 is set and
supply of material to the crushing gap 6 of the crusher is commenced. The supplied
material is crushed in the gap 6 and may then be collected vertically below the same.
According to the present invention, a representative value is calculated,
which, is representative of the highest measured instantaneous loads on the crusher. As
used in the present application, "load" relates to the stress that the crusher is exposed to on
a certain occasion. The load may., according to the present invention, for instance, be
expressed in the form of a mean peak pressure, which is calculated from hydraulic fluid

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pressures as measured by the pressure transducer 13. The load may also be expressed as a
mean peak motor power that is calculate d from motor powers 35 measured by the
transducer 12, or as a mean peak tension that is calculated from mechanical tensions in the
crusher as measured by a tension sensor, for instance a strain gauge.
Fig 2 schematically shows a method for controlling the operation of the
crusher depending on the hydraulic fluid pressure. The crushing process results in a
varying pressure arising in the hydraulic fluid. At a certain quantity of supplied material of
a certain hardness and size, a narrow gap 6 will mean a high hydraulic fluid pressure and a
wide gap 6 will mean a low hydraulic fluid pressure. A high mean hydraulic fluid pressure
means that the crusher is utilized efficiently in order to crush the supplied material. Thus,
it is desirable that for a certain quantity of supplied material keep as high mean pressure as
possible without the crusher risking to be damaged mechanically. In the step 20 shown in
Fig. 2, measurement is commenced of the instantaneous hydraulic fluid pressure in the
adjusting device 7, 8, 9, 15 by means of the pressure transducer 13, The measurement of
the instantaneous hydraulic fluid pressure started in step 20 continues as long as the
crusher is in operation. The signal from the pressure transducer 13 is received by the
control device 11. In step 22, the supply of material to the crusher is commenced. In step
24, the highest hydraulic fluid pressure that has been receded during a period of time of
0.2 s is stored in the control device 11. The highest hydraulic fluid pressure measured in
step 24 forms, together with the correspond ing values for the four closest preceding
periods of time, a sequence of repeated measurements of highest hydraulic fluid pressures,
hi step 26. a representative value is calculated in the form of a mean peak pressure as a
mean value of the highest hydraulic fluid pressures included in said sequence, which thus
have been measured during each one of the five periods of time which are contained
within the latest 1.0 s. Said mean peak pressure is thereby a value that is representative of
(he highest measured instantaneous hydraulic fluid pressures. The calculated mean peak
pressure is compared with a desired value in step 28, the difference between the mean peak
pressure and the desired value being calculated. The difference between the desired value
and the calculated mean peak pressure obtained in step 28 is utilized in step 30 in order to
determine if the pump 8 should reduce or increase the hydraulic fluid pressure in the
adjusting device, the period of time the pump should be in operation and if any time
should pass before a pressure alteration should be started. In step 32, the control device 11
emits a control signal to the pump 8, if the conditions for such a control signal are met and
a new sequence of measurements is initiated by step 24 again being commenced When the
hydraulic fluid pressure is increased or reduced the shaft 1, and thereby the inner shell 4,
will be raised or lowered, the gap 6 becoming more slender or wider, respectively. Thus,

1 3
the hydraulic pressure alteration will affect the width of the gap 6 and thereby the load on
the crusher.
The occasions when the pump 8 should be taken into operation, "pump", and how
long it should pump hydraulic fluid to or from the piston 15, is thus controlled by the
control device 11, The pumping takes place during a certain space of time, the length of
which is proportional in steps to the difference between the current mean peak pressure
and the desired value, i.e., if the current mean peak pressure is within a certain interval at a
certain distance from the desired value, pumping is effected during a certain time, while if
the current mean peak pressure is in an interval which is closer to the desired value, the
pumping is effected during a shorter space of time.
Fig, 3 schematically shows a curve P of measured hydraulic fluid pressure during a
period of 2 s. Within each period of time of 0.2 s, the highest hydraulic fluid pressure is
recorded during that period of time. In Fig 3, the periods of time have been numbered from
1 to 10 and the highest hydraulic fluid pressure in each period of time, which hydraulic
fluid pressure is stored in the control device 11 in step 24, has for period of time 1 to 5
been marked with an arrow. The mean peak pressure mentioned in step 26 is calculated as
a mean value of the highest hydraulic fluid pressures from the respective period of time 1
to 5, which are included in a first sequence S1 of repeated measurements of highest
hydraulic fluid pressures. In the iteration following next, i.e., when step 24 again has been
commenced, the highest hydraulic fluid pressure in period of time no. 6 will be stored in
the control device 11, a new mean peak pressure being calculated from the highest
hydraulic fluid pressures from the respective period of time 2 to 6, which are included in a
second sequence S2 and so on. Thus, a new mean peak pressure will be calculated five
times per second and said mean peak pressure will be based on the respective highest
hydraulic fluid pressures which have been measured during the five latest periods of time.
Fig. 4 schematically shows an even more preferred embodiment, wherein a
sifting of the respective highest hydraulic fluid pressures is made before a mean peak
pressure is calculated. In this even more preferred method, step 26 has been configured
according to the following. The respective highest hydraulic fluid pressures from the latest
10 periods of time are compared, the two highest values and the five lowest values being
sifted away. A mean peak pressure is then calculated as a mean value of the remaining 3
periods of time and is utilized in step 28. Fig 4 shows a schematic illustration of how the
sifting has taken place in 3 sequence S3 of repeated measurements of highest hydraulic
fluid pressures. The periods of time which have the two highest and the five lowest values,

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respectively, of highest hydraulic fluid pressure have been sifted away, which is
symbolized, by they having been crossed over in Fig. 4. Thanks to the fact that more of the
lowest than of the highest values of highest hydraulic fluid pressure are excluded, the mean
peak pressure, which later is correlated to the desired value, will be more sensitive to the
highest pressures. Thus, the control system will react faster on pressure increases than on
pressure reductions, which decreases the risk of mechanical breakdowns caused by too
high pressures. Thus, the mean peak pressure is calculated as a mean value of the highest
hydraulic fluid pressures during those periods of time of the periods of time 1 to 10 that
have not been silled away. Table 1 below indicates how the analysis, which lakes place in
the control device 11, may look like:

The control device 11 suitably also measures the mean hydraulic fluid
pressure. The mean hydraulic fluid pressure is a measure of the load of the crusher and
should be as high as possible. In Fig- 3 and Fig. 4, the mean hydraulic fluid pressure has
been marked with a dashed curve A. Thus, the mean hydraulic fluid pressure is an average
of all measured instantaneous hydraulic fluid pressures during the preceding 2.0 s. In
efficient operation of the crusher, the mean hydraulic fluid pressure, i.e., curve A, should
be close to the calculated mean peak pressure, i.e., the mean value of the highest hydraulic
fluid pressures measured during respective period of time. Accordingly, it is desirable to
keep the hydraulic fluid pressure on an even and high level. In such an operation, the
crusher will be utilized maximally for crushing without the risk of increasing mechanical
breakdowns,

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Fig. 5 shows a typical geometry of a hydraulic pressure curve P in an
efficiently operating crusher. In this case, the desired value of mean peak pressure was
predetermined to 5.0 MPa. The mean peak pressure M varies between approx. 4.5 and 5.5
MPa As is seen in Fig. 5, the mean hydraulic fluid pressure A is approx. 4 MPa, i.e., only
somewhat below the calculated mean peak pressure M. This is provided by the fact that the
supply of material to the crusher is handled in such a way that the flow of material is even
and contains material having approximately the same size distribution, moisture content
and hardness.
Fig. 6 shows a typical geometry of a hydraulic fluid pressure curve P for a
crusher of the same type as above but at substantially varying load, which, for instance,
may depend on the amount of material and/or the size distribution of the material varying
relatively much. The desired value of mean peak pressure was aiso in this case 5.0 MPa.
The mean peak pressure M varies between approx. 4.5 and 5.5 MPa. Thus, the control
device 11 can, also on substantially varying load, keep the mean peak pressure M within
narrow margins, wherein mechanical breakdowns may be avoided also, for instance, upon
uneven supply and operational disturbances. As is seen in Fig. 6, the mean hydraulic fluid
pressure A is on approx. 3.2 MPa, which is considerably below the mean peak pressure M
and, therefore, the crusher operates with relatively low efficiency,
Fig, 7 shows a pointer instrument 40, which visually shows how efficiently the
operation of the crusher is. The pointer instrument 40 has a dial 42 and two pointers in the
form of needles 44,46. A first needle 44 shows a comparative value in the form of the
mean hydraulic fluid pressure in the crusher. A second needle 46 shows a representative
value in the form of the mean peak pressure, i.e., the mean value of the highest hydraulic
fluid pressures that have been measured during a number of periods of time, which
accordingly is a value which is representative of the highest measured instantaneous
hydraulic fluid pressures and which has been calculated according to the above. The
distance between the first needle 44 and the second needle 46 is an indication of how
efficiently the crusher operates. The desired value of the mean peak pressure has been
marked with a line 48 on the dial 42 of the pointer instrument. In the position that is shown
in fig. 7, the mean peak pressure, which is shown by the second needle 46, is incidentally
lower than the desired value. Thus, the control device 11 will instruct the pump 8 to pump
in more hydraulic fluid so that the crushing head 3 is raised and the hydraulic fluid
pressure increases again.

1.6
In Fig. 7, a third pointer is also shown in the form of a dashed third needle 50 ,
which is included in an alternative design at the pointer instrument 40. The needie 50 is
utilized in order to show a. difference calculated by the control device 11 between the mean
hydraulic fluid pressure and the mean peak pressure with the purpose of more clearly
illustrating how efficiently the crusher operates.
In Fig. 7. also a fourth pointer is shown in the form of a dashed and dotted fourth
needle 52, which is included in an additional alternative design of the pointer instrument
40. The needle 52 is utilized in order to show a comparative value calculated by the
control device 11 in the form of a mean bottom pressure. The mean bottom pressure is
ealculated according ro the same principle as has been described above for the mean peak
pressure, but is instead based on the lowest measured hydraulic fluid pressures. Thus, the
mean bottom pressure is calculated as a mean value of the lowest hydraulic fluid pressures
that have been measured during a number of consecutive periods of time, and thereby
represents the lowest loads on the crusher. The distance between the fourth needle 52,
which shows the mean bottom pressure, and the second needle 46, which shows the mean,
peak pressure, thus illustrates how large the variation in load on the crusher is. The fourth
needle 52 may he used together with the first needle 44, which shows the mean pressure,
or replace the same, wherein the needle 52 will work as a first pointer that then, together
with the second needle 46, which shows the mean peak pressure, illustrates the operation
condition in the crusher, It is also possible to calculate the difference between the mean
peak pressure and the mean bottom pressure and let a fifth pointer, not shown in Fig. 7,
show this difference.
Fig. 8a shows another embodiment hi the form of a pointer instrument 140. The
same pointer instrument 140 is formed as a virtual window, which is shown on a display
device, for instance a display device included in the control device 11. The pointer
instrument has a dial 142, a first pointer 144, which shows the mean hydraulic fluid
pressure, and a second pointer 146, which shows the mean peak pressure, i.e., the mean
value of the highest hydraulic fluid pressures which have been measured during a number
of periods of time- The first and the second pointer 144 and 146, respectively, form
between themselves a sector 150 that has another color, for instance black, than the dial
142 find therefore is clearly seen- Thus, the extension of the sector 150 on the dial 142
becomes a visually easy-to-read measure of how efficiently the crusher operates. The
position of the first pointer 144 is updated each time a new mean hydraulic fluid pressure
has been calculated and the position of the second pointer 146 is updated each time a new
mean peak pressure has been calculated. The pointer instrument 140 shown in Fig. 8a

17
illustrates the condition in the crasher, the hydraulic fluid pressure curve P of which is
shown in Fig. 5, i.e., an efficiently operating crusher,
The pointer instrument 140 has also a virtual display 152 that, tor instance, may
display the current mean peak pressure, mean hydraulic fluid pressure or the difference
between these pressures.
In Fig. 8b, a pointer instrument 140 is shown of the same type as the one shown in
Fig. &a. However, the pointer instrument 140 shown in Fig. 8b illustrates the condition in
the crusher, the hydraulic fluid pressure curve P of which is shown in Fig. 6, i.e., a crusher
which does not operate efficiently by virtue of substantially varying load. As is seen in Fig.
8b, the sector 150 has a large extension on the dial 142 since the mean hydraulic fluid
pressure, which is shown by the pointer 144, is considerably lower than the mean peak
pressure, which is shown by the pointer 146, which clearly indicates to the operator that
measures needs to be taken in order to increase the efficiency of the crusher.
Fig, 9 schematically shows a gyratory crusher that is of another type than the
crusher shown in Fig. 1. The crusher shown in Fig. 9 has a shaft 201, which carries a
crushing head 203 having a first crushing means in the form of an inner crushing shell 204
mounted thereon. Between the inner shell 204 and a second crushing means in the form of
an outer crushing shell 205, a crushing gap 206 is formed. The outer crushing shell 205 is
attached to a case 207 that has a trapezoid thread 208, The thread 208 mates with a
corresponding thread 209 in a crusher frame 216. Furthermore, a motor 210 is connected
to the crusher, which is arranged to bring the shaft 201, and thereby the crushing head 203,
to execute a gyratory movement during operation. When the ease 207 is turned by an
adjustment motor 215 around the symmetry axis thereof, the outer crushing shell 205 will
be moved vertically, the width of the gap 206 being changed. In this type of gyratory
crusher, accordingly the case 207, the threads 208,209 as well as the adjustment motor
215 constitute a adjusting device for adjusting of the width of the gap 206, Upon control of
the load on a crusher of this type by means of a control device 211, it is according to the
invention possible to utilize a transducer 212, which measures the instantaneous power
generated by the motor 210. From the highest measured powers during a number of
periods of time, subsequently a mean peak power may be calculated and compared with a
desired value. Depending on said comparison, the load on the crusher is controlled. The
same control may, for instance, consist of the adjustment motor 215 being instructed to
time the case 207 in order to alter the width of the gap 206. ti is also possible to alter the

18
supply of material, the number of revolutions of the motor 210 and/or the stroke of the
shaft 201 in the horizontal direction.
An alternative method to measure the load, which method works both in crushes
having hydraulic adjusting devices and crushes of the type which is shown in Fig. 9, is to
measure a mechanical stiess or tension in the proper crusher. As is seen in Fig. 9, a strain
gauge 213 has been placed on the crusher frame 216. The strain gauge 213, which
measures the instantaneous strain in the part of the frame 216 to which it is attached, is
suitably placed on a location on the frame 216 which gives a representative picture of the
mechanical load on the crusher- From the highest measured strains, possibly converted to
corresponding tensions, during a number of periods of time, a mean peak strain or tension
may then be calculated and utilized in order to control the load on the crusher.
Fig. 10 schematically shows a jaw crusher. The jaw crusher has a frame 316 and a
movable jaw 303 movably mounted therein. The movable jaw 303 carries a first crushing
means in the form of a first crushing plate 304. The frame 316 carries a second crushing
means in the form of a second crushing plate 305. A crushing gap 306 is formed between
the first crushing plate 304 and the second crushing plate 305. The jaw 303 is rotatably and
eccentrically secured at its upper end to a flywheel 30 L The flywheel 301 is driven via a
belt 302 by a driving device in the form of a motor 310 and thereby gets the upper portion
of the jaw 303 to describe a substantially elliptical movement, which causes material fed
into the gap 306 to be crushed by the crushing plates 304, 305. The lower end of the jaw
303 is supported by a toggle plate 307. The toggle plate 307 has a hydraulic cylinder 308,
which makes it possible to adjust the width of the gap 306. At this type of crusher the
toggle plate 307 and (he hydraulic cylinder 308 an adjusting device for adjustment of the
width of the gap 306. At control of the load on a crusher of this type by means of the
control device 311 it is according to the present invention possible to use a gauge 312 that
measures the instantaneous povveT that develops at the motor 310 and sends a signal to the
control device 311 A mean peak power can then be calculated from the highest measured
powers during a number of periods of time in accordance with what has been described
above and be compared to a desired value. The load on the crusher is controlled depending
of this comparison. This control may for example consist in the control device 311 orders
the hydraulic cylinder 308 to change the width of the gap 306. It is also possible to order
change of feed of material to the crusher or of the rotational speed of the motor 310.
It is also possible to measure e mechanical load or tension in the crusher itself. As
is apparent from Fig. 10 a strain gauge 313 has been positioned on the crusher frame 316.

19
The strain gauge 313 that measures the instanlaneous strain in the portion of the frame 316
on which it is secured, can be used in a similar way as described above regarding the gauge
213. Another possibility is to position a strain gauge 314 on the toggle plate 307 for
measuring the instantaneous load on the toggle plate 307 and to send a signal to the control
device 311 that uses that signal for controlling the crusher. It is also possible to measure
the hydraulic fluid pressure in the hydraulic cylinder 308 of the toggle plate 307 and to use
said pressure as a measure on the load on the crusher. It is understood that the toggle plate
307 is schematically shown and that other devices and other types of toggle plates may be
used for adjusting the width of the gap 306.
It will be appreciated that a number of modifications of the above-described
umbodiments are feasible within the scope of the invention, such as it is defined by the
appended claims,
The representative value that is representative of the highest measured
instantaneous loads may, for instance, be calculated as a mean peak pressure according to
what has been described above. There are, however, a plurality of other methods to
calculate said representative value. For instance, a standard deviation from the mean load
may be calculated and utilized ss said value. A small standard deviation is then an
indication of the crusher operating efficiently. An additional alternative is to take both the:
height and duration of the respective load peak into consideration. For instance, the
extension of the peaks In time and height may be calculated by integration, said value
being calculated as a mean value of a number of integrated peaks.
Two consecutive sequences of data may either partly overlap each other, such as
has been described above, or follow immediately upon each other insiead of partly
utilising the same data.
It will be appreciated that a person skilled in the art by experiments can derive
lengths of the periods of time suitable for certain specific operation conditions, how many
periods of time that should be included in a sequence, how many data in a sequence that
should be retrieved from a preceding sequence and if any data should be sifted away before
calculation of mean values and that the above-described statements constitute a preferred
example. For instance, a suitable kngth of each period of time has turned out to be 0:05 to
1.s.

20
Above is described how the control device 11 controls the hydraulic fluid pressure
depending on a comparison of said representative value, which, for instance, may be a
mean peak pressure, with a desired value of the pressure. However, the control device 11
may also be arranged to lake the load of the motor 10 into consideration. If the signal from
the transducer 12, which measures the load of the motor 10, indicates that the load oa the,
motor 10 exceeds an allowed load value, the control device 11 will instruct the pump 8 to
decrease the hydraulic fluid pressure, also if the mean peak pressure does not exceed the
desired value of pressure, in order to avoid overload of the motor 10.
Above a method for controlling the crusher is described where it is desirable to
keep highest feasible load and size reduce the material as much as possible. The control
device 11 aims, in that connection, at keeping a high hydraulic fluid pressure and makes
this by continuously keeping the gap 6 as narrow as possible, the supplied material being
exposed to a maximum size reduction. In certain cases, il is instead ofinterest to keep a
fixed width of the gap 6 in order to provide a certain size of the crushed product, In such a
case, the control device 11 ean instead be utilized as a safety function that incidentally
increases the gap somewhat in order to reduce the hydraulic fluid pressure when the
calculated mean peak pressure during any shorter period exceeds the desired value of
pressure. Therefore, in this way, a larger quantity of supplied material can be crushed to a
certain desired size without risk of mechanical breakdown. It also becomes considerably
simpler to maximize the quantity of material that can be crushed to the desired size. An
additional possibility is to let the crusher altematingly operate in control towards
maximum load and in control to a fixed gap. It is also possible to keep the width of the gap
6 constant and instead control the load on the crusher by means of some other parameter,
for instance the amount of supplied material.
It is understood the width of the crushing gap 6,206, 306 can be adjusted in
different ways and that the above-described methods, reference being had to Figs. 1, 9 and
10, are non-limiting examples.
The above-described pointer instruments 40; 140 are provided with needles 44,46
and pointers 144,146, respectively, which may be mechanical or be shown on a display
device. It is however also possible instead to utilize digital display of the actual numbers
concerning the mean hydraulic fluid pressure and mean peak pressure, which have been
calculated. Thus, in this case, the pointer of the pointer instrument will consist of displays
that, suitably digitally, show calculated numbers. It is, as is mentioned above, also possible
to calculate the difference between the mean hydraulic fluid pressure and the mean peak

21
pressure and let a third pointer, which may be a needle 50 or a display showing the number
in question, show said difference. The difference between mean hydraulic fluid pressure
and mean peak pressure may thereby be used, for following-up of the operation of the
crusher- a small difference meaning, as mentioned above, that the crusher operates effi-
ciently- It is also possible to combine display with needles and display of numbers in
question and to in that connection utilize needles in order to show mean hydraulic fluid
pressure and mean peak pressure and a display in order to show the calculated difference
between the same.
It is also possible to form a pointer instrument having a sector that is formed
between a second pointer, which shows the mean peak pressure, and a fourth pointer,
which shows the mean bottom pressure. A first pointer, which shows the mean pressure,
may be imparted another color than the sector and is placed on top of the same in order to
also show the mean pressure in the adjusting device.

22
We Claim :
1. Method for controlling a crusher, at which material to be crushed is inserted into a gap
(6; 206; 306} between a first crushing means (4; 204; 304) and a second crushing means
(5; 205; 305), characterized by the following steps
a) that the instantaneous load on the crusher is measured during at ieast one
period of time to obtain a number of measured values,
b) that a representative value, which is representative of the highest measured
instantaneous load during each such period of time, is calculated, and
c) that the representative value is compared to a desired value and that the
load on the crusher is controlled depending on said comparison.

2. Method according to claim 1, wherein step a) also comprises that a. sequence of data is
formed, which data consist of determinations of the highest load on the crusher in each one
of said periods of time, which consist of a plurality of consecutive periods of lime.
3. Method according to claim 2, wherein said representative value is calculated in step b)
as a mean value of data included in said sequence.
4. Method according to claim 2 or 3, wherein said periods of time follow immediately after,
each other,
5. Method according to any one of claims 2-4, wherein said measured values are
processed continuously during operation of the crusher for forming a plurality of
sequences of data.
6. Method according to claim 5, wherein upon calculation of said representative value of a
current sequence, at least one data is utilized concerning highest load which already has
been utilized in an immediately preceding sequence.
7. Method according to any one of claims 4-6, wherein all sequences include the same
number of data concerning highest load and that said data amounts to at least five for each
sequence.

23
8. Method according to any one of claims 2-7, wherein at least the highest value of data
included in the sequence concerning highest load is excluded upon calculation of said
representative value of said sequence.
9. Method according to any one of claims 2—8, wherein at least the lowest value of the data
included in the sequence concerning highest load is excluded upon calculation of said
representative value of said sequence,
10. Method according to any one of claims 2-9, wherein at least the highest as well at least
the two lowest values of the data included in the sequence concerning highest load are
excluded upon calculation of said representative value of said sequence, more of the
lowest than of the highest values being excluded,
11, Method according to any one of the preceding claims, wherein the width of the gap (6;
306) is adjustable by means of a hydraulic adjusting device (7, 8 ,9,15; 307,308), and
wherein in step a) the load is measured as a hydraulic fluid pressure m said device,
12. Method according to any one of claima 1—10, wherein in step a) the load is measured
as the power of the driving device (10:210; 310).
13. Method according to any one of claims 1-10, wherein in step a) the load is measured
as a mechanical stress on the crusher.
14. Method according to any one of claims 1-13, wherein in step a) the load is measured
as at least two of the parameters hydraulic fluid pressure in a hydraulic adjusting device (7,
8 ,9,15; 307,308), the power of the crusher driving device (10; 210; 310) and a
mechanical stress m the crusher, wherein the one of the above-mentioned parameters
which is highest in relation to the desired value thereof being utilized in step c).
15. Method according to any one of claims 1-14, wherein in step c) the load is controlled
by at least one of the following steps being carried out;
that the width of the gap (6; 206; 306) is changed,
that the supply of material to the gap (6; 206; 306) is changed,
that the number of revolutions of the rotational speed for a crusher driving
device (10;210;310) is adjusted, and
that the mutual movements of the crushing means (4.5; 204,205; 304, 305)
are adjusted.

24
16. Pointer instrument for indication of load on a crusher, comprising a first crushing
means (4; 204; 304) and a second crushing means (5; 205; 305), a gap (6; 206; 306)
between said crushing means (4, 5; 204,205; 304, 305) being provided to receive material
to be crushed,
characterized in that the pointer instrument (40; 140) has
a first pointer (44,52; 144), which shows a comparative value, and
a second pointer (46; 146), which shows a representative value, which has
been determined after the instantaneous load on the crusher in a step a) has been measured
during at least one period of time to obtain a number of measured values, said
representative value in a step b) having been calculated as being representative of the high-
est measured instantaneous load during each such period of time, said comparative value
being determined depending on the load on the crusher such that a comparison between the
position of the first pointer (44, 52; 144) and the position of the second pointer (46; 146)
give an indication whether the operation of the crusher is effective.
17. Pointer instrument according to claim 16. wherein step a) also comprises that a
sequence of data has been formed, which data consist of determinations of the highest,
measured Joad on the crusher in each one of said periods of time, which consist of a
plurality of consecutive periods of time, said representative value in step b) having been
calculated as a mean value of data included in said sequence.
18. Pointer instrument according to any one of claims 16—17, the first and the second
pointer (144, 146) forming sides of a sector (150), the extension of which indicates the
operation. conditions of the crusher.
19. Pointer instrument according to any one of claims 16-18, which has a third pointer
(50) for display of a calculated difference between the comparative value and said
representative value.
20. Pointer instrument according to any one of claims 16-19, wherein the first pointer (44;
144) shows a comparative value that represents the average load on the crusher.
21, Pointer instrument according to any one of claims 16-19, wherein the first pointer (52)
shows a comparative value, which has been determined after the instantaneous load on the
crusher in a first step has been measured to obtain a number of measured values, said

25
comparative value in a second step having been calculated as being representative of the
lowest measured instantaneous load during each such period of time.
22, Control system for controlling the load in a crusher, which comprises a first crushing
means (4; 204; 304) and a second crushing means (5; 205; 305), a gap (6; 206; 306)
between said crashing means (4, 5; 204,205; 304,305) being provided to receive material
1o be crushed,
characterized in that the control system comprises
a measuring device (12; 212; 312; 13; 213; 313; 314), which is arranged to
measure the instantaneous load on the crusher during at least one period of time to obtain a
number of measured values,
a calculation device (11; 211; 311), which is arranged to calculate a
representative value which is representative of the highest measured instantaneous load
during such period of time, and
a control device (11; 211; 311), which is arranged to compare said
representative value with a desired value and to control the load on the crusher depending
on said comparison.
23. Control system according to claim 22, wherein the calculation device (11; 211; 311) is
arranged to firstly process the measured values to obtain at least one sequence of data,
which consists of determinations of the highest load on the crusher in each one of a
plurality of consecutive periods of time, the calculation device (11;211;3ll) being
arranged to subsequently calculate said representative value as a mean value of data
included in said sequence.


A crusher has a first crushing means (4) and a second crashing means (5) together
with the first crushing means (4) defining a crushing gap (6). A measuring device (12, 13)
is arranged to measure the instantaneous load on the crusher during at least one period of
time to obtain a number of measured values. A calculation device (11) is arranged to
calculate a representative value that is representative of the highest, measured
instantaneous load during each such period of time, A control device (11) is arranged to
compare the representative value with a. desired value and to control the load on the
crusher depending on said comparison. In this type of control; a more efficient crushing
and reduced risk of the crusher breaking down are obtained.

Documents:


Patent Number 216054
Indian Patent Application Number 01325/KOLNP/2005
PG Journal Number 10/2008
Publication Date 07-Mar-2008
Grant Date 06-Mar-2008
Date of Filing 11-Jul-2005
Name of Patentee SANDVIK INTELLECTUAL PROPERTY AB
Applicant Address S-811 81 SANDVIKEN, SWEDEN
Inventors:
# Inventor's Name Inventor's Address
1 NILSSON MATTIAS KARRBY GARD, S-275 94 SJOBO, SWEDEN.
2 NILSSON, ANDERS LOTSGATAN 145,S-26143 LIMHAMN, SWEDEN.
3 GULLANDER, JOHAN OSTRA RYTTMASTAREGATAN 11B,S-217 52 MALMO, SWEDEN.
4 SVENSSON, KJELL-AKE NORRA HYLLIEVAGEN 62, S-216 17 LIMHAMN, SWEDEN.
5 NILSSON, KENT KOPENHAMNSVAGEN 41C, S-217 71 MALMO, SWEDEN.
PCT International Classification Number B02C 1/02
PCT International Application Number PCT/SE2004/000162
PCT International Filing date 2004-02-09
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0300327-4 2003-02-10 Sweden