Abstrict A crusher includes a replaceable first crushing member having a
first crusher surface and a replaceable second crushing member having
a second crusher surface. The co-operation of the crusher surfaces
is defined by at least one crusher setting parameter. From measurements
of a quality parameter, which relates to the nature of the crushed
material, on at least two different occasions during the service
life of a set of replaceable first and second crushing members and
on each occasion for at least two different settings of the crusher
setting parameter, a control function can be determined that describes
a value, of the at least one crusher setting parameter, which on
a given occasion gives a crushed material the quality parameter
of which is substantially optimal. The control function is utilized
for the adjustment of the crusher setting parameter for a subsequent
set of replaceable first and second crushing members in such a way
that on a given occasion for the subsequent set of replaceable crushing
members, a crushed material is also obtained, the quality parameter
of which is substantially optimal.
Claims 1. A method to control a crusher which comprises a replaceable
first crushing member having a first crusher surface and a replaceable
second crushing member having a second crusher surface, which crushing
members are arranged to be brought toward each other in a reciprocating
motion and between one another crush a material that passes between
the crusher surfaces in a direction having a vertically downwardly
directed direction component, said method comprising: defining the
co-operation of the crusher surfaces by at least one crusher setting
parameter, measuring at least one quality parameter, which relates
to the nature of the crushed material, on at least two different
occasions during the service life of at least one set of replaceable
first and second crushing members and on each occasion for at least
two different settings of the crusher setting parameter, and utilizing
the measured quality parameter for said set of replaceable crushing
members for determining a control function that describes a value,
of said at least one crusher setting parameter, which on a given
occasion gives a crushed material the quality parameter of which
is substantially optimal, and utilizing the control function for
adjusting the crusher setting parameter for a subsequent set of
replaceable first and second crushing members in such a way that
on a given occasion for the subsequent set of replaceable crushing
members, a crushed material is obtained said quality parameter of
which being substantially optimal.
2. The method according to claim 1 wherein determining the control
function includes selecting a criterion, which defines what is an
optimum quality parameter, and determining the values of the crusher
setting parameter that best fulfil said criterion from the quality
parameters measured on the respective occasions, and determining
the control function as a curve fitted to said values of the crusher
setting parameter.
3. The method according to claim 1 further comprising measuring
quality parameters for at least two different sets of replaceable
crushing members and utilizing the measured quality parameters for
said at least two different sets of replaceable crushing members
for determining the control function.
4. The method according to claim 1 further comprising measuring
at least one quality parameter, which relates to the nature of the
crushed material, on at least three different occasions and utilizing
the measured quality parameters for determining the control function.
5. The method according to claim 1 wherein each measurement is
carried out for at least three different settings of the crusher
setting parameter.
6. The method according to claim 1 further comprising extrapolating
the control function in order to cover the entire time during which
the subsequent set of replaceable crushing members are used.
7. The method according to claim 1 further comprising selecting
said at least one crusher setting parameter from the group consisting
of: the shortest distance between the first crusher surface and
the second crusher surface, the power generated by a motor driving
the crusher, the quantity of material fed into the crusher, the
rotation speed of a shaft rotating a crushing head in a gyratory
crusher, the horizontal stroke of a lower end of the shaft in the
gyratory crusher, the pressure by which the shaft in the gyratory
crusher loads a setting device that sets the position of the shaft
in the vertical direction, the rotation speed of a flywheel driving
a movable jaw in a jaw crusher, and the horizontal stroke of the
lower end of the movable jaw in a jaw crusher.
8. The method according to claim 7 wherein said selecting at least
one crusher setting parameter comprises selecting a parameter that
describes the shortest distance between the first crusher surface
and the second crusher surface.
9. The method according to claim 1 further comprising selecting
said at least one quality parameter of the crushed material from
the group consisting of: grain shape, size distribution, strength
value, quantity of crushed material per time unit, and quantity
of crushed material per energy unit.
10. The method according to claim 1 wherein said given occasion
includes a given operating time, a given quantity of material having
been crushed, or a given quantity of energy having been consumed
in the crushing.
11. A crusher comprising: a replaceable first crushing member having
a first crusher surface and a replaceable second crushing member
having a second crusher surface, said crushing members being arranged
to be brought toward each other in a reciprocating motion and so
as to crush therebetween a material that passes between the crusher
surfaces in a direction having a vertically downwardly directed
direction component, wherein cooperation of the crusher surfaces
is defined by at least one crusher setting parameter; a control
device utilizing at least one measured quality parameter, which
relates to the nature of the crushed material and which has been
measured on at least two different occasions during the service
life of at least one set of replaceable first and second crushing
members and on each occasion for at least two different settings
of the crusher setting parameter, to determine a control function
that describes a value of said at least one crusher setting parameter,
which on a given occasion gives a crushed material the quality parameter
of which is substantially optimal, and to utilize the control function
to adjust said at least one crusher setting parameter for a subsequent
set of replaceable first and second crushing members in such a way
that on a given occasion for the subsequent set of replaceable crushing
members, a crushed material may be obtained said quality parameter
of which is substantially optimal.
12. A control system for the control of a crusher which comprises
a replaceable first crushing member having a first crusher surface
and a replaceable second crushing member having a second crusher
surface, said crushing members being arranged to be brought toward
each other in a reciprocating motion and so as to crush therebetween
a material that passes between the crusher surfaces in a direction
having a vertically downwardly directed direction component, the
control system comprising: a control device, utilizing at least
one measured quality parameter, which relates to the nature of the
crushed material and which has been measured on at least two different
occasions during the service life of at least one set of replaceable
first and second crushing members, wherein the cooperation of the
crusher surfaces is defined by at least one crusher setting parameter,
and on each occasion for at least two different settings of said
crusher setting parameter, to determine a control function that
describes a value of said at least one crusher setting parameter,
which on a given occasion gives a crushed material the quality parameter
of which is substantially optimal, and utilize said control function
for the adjustment of said at least one crusher setting parameter
for a subsequent set of replaceable first and second crushing members
in such a way that on a given occasion for the subsequent set of
replaceable crushing members, a crushed material can be obtained
said quality parameter of which is substantially optimal.
Description TECHNICAL FIELD
[0001] The present invention relates to a method to control a crusher,
which comprises a replaceable first crushing member having a first
crusher surface and a replaceable second crushing member having
a second crusher surface, which crushing members are arranged to
be brought toward each other in a reciprocating motion and between
themselves crush a material that passes between the crusher surfaces
in a direction having a vertically downwardly directed direction
component.
[0002] The invention also relates to a crusher, which is of the
type gyratory crusher or jaw crusher and comprises the replaceable
crushing members mentioned above.
[0003] The invention also relates to a control system for the control
of a crusher, which is of the kind mentioned above.
BACKGROUND OF THE INVENTION
[0004] When crushing a hard material, for instance stone or ore,
a crusher having a crushing gap, also called crushing chamber, is
frequently utilized, where material is fed in from above and is
crushed between two crusher surfaces that are brought toward each
other and between which the hard material is crushed. An example
of such a crusher is a gyratory crusher, which has a crushing head
provided with an inner crushing shell, which head is fastened on
a shaft and during operation describes a gyratory motion, and an
outer crushing shell surrounding the inner crushing shell. The fed-in
material is then crushed in a plurality of steps between the inner
and outer shell. An additional example of a crusher of the type
mentioned above is a jaw crusher in which a fed-in material is crushed
between a fixed first jaw plate and a second jaw plate mounted on
a movable jaw, which second jaw plate moves toward the first jaw
plate in a reciprocating motion and in a plurality of steps successively
crushes a fed-in material.
[0005] After a time of operation, crushing gives rise to wearing
of the crusher surfaces and an increased distance between them.
WO 93/14870 describes a method to compensate for this wear. In the
method described in WO 93/14870 the shortest distance between the
inner shell and the outer shell is calibrated on a plurality of
occasions during the service life of a first pair of shells. Based
on the same data, it is possible to predict how this shortest distance
will be altered over time for a new pair of shells and to compensate
for this alteration so that the shortest distance between the inner
and outer shell in said new pair of shells is kept substantially
constant during the entire service life of the shells.
[0006] However, the above-described method of compensating for
wear has the disadvantage that it cannot produce a crushed material
having predictable properties during the service life of a pair
of shells.
SUMMARY OF THE INVENTION
[0007] It is an object of the present invention to provide a method
to compensate for wear in a crusher, which method entails that the
crushed material will have predictable properties during the service
life of a pair of crusher surfaces.
[0008] This object is attained by a method according to the preamble,
surfaces is defined by at least one crusher setting parameter, that
at least one quality parameter, which relates to the nature of the
crushed material, is measured on at least two different occasions
during the service life of at least one set of replaceable first
and second crushing members and on each occasion for at least two
different settings of the above-mentioned crusher setting parameter,
and that the measured quality parameter for said set of replaceable
crushing members is utilized for the determination of a control
function that describes the value of the crusher setting parameter
that on a given occasion gives a crushed material the quality parameter
of which is substantially optimal, and that this control function
is utilized for the adjustment of the crusher setting parameter
for a subsequent set of replaceable first and second crushing members
in such a way that on a given occasion for the same subsequent set
of replaceable crushing members, a crushed material is provided
said quality parameter which is substantially optimal.
[0009] An advantage of this method is that measurements that are
made for a set of replaceable crushing members can be utilized for
making sure that the crushed material for a subsequent set of crushing
members gets optimally good properties without any, or at least
no more than one or a few, measurements needing to be made during
operation using the same subsequent set. Thus, a crushed material
of optimum nature according to the criteria set up can be obtained,
with a minimum of effort in the form of measurements. This is especially
advantageous when the material that should be crushed has similar
properties over a long period of time. One example is crushing in
connection with mining, where the fed-in material may have similar
properties during a plurality of years and where, during this period,
a great number of sets of replaceable crushing members are consumed.
In the method, a compensation is obtained for the effect of the
wear on the geometry of the crushing gap, also called crushing chamber,
that is formed between the two crusher surfaces. Contrary to the
known technique, where compensation solely takes place for the alteration
of the shortest distance between the crusher surfaces, according
to a preferred embodiment of the invention, a compensation is obtained
for the geometrical alteration of the entire crushing gap and, thereby,
also for how this geometrical alteration will effect the nature
of the crushed material.
[0010] Conveniently, the determination of the control function
involves that a criterion, which defines what is an optimum quality
parameter, is selected, that the values of the crusher setting parameter
that best fulfil the same criterion is determined from the quality
parameters measured on the respective occasions, and that the control
function is determined as a curve fitted to these values of the
crusher setting parameter. The fitted curve entails that a few measurements
are enough for the provision of a control function that on an arbitrary
occasion during the service life of a subsequent set of replaceable
crushing members gives the value of the crusher setting parameter
that on this arbitrary occasion gives a substantially optimum quality
parameter, i.e., a maximum compliance with the chosen criterion.
It will be appreciated that the chosen criterion does not need to
have been the exact subject of the measurements, but it is enough
that values of the chosen criterion can be determined from the data
having been measured.
[0011] According to a preferred method, quality parameters are
utilized that have been measured for at least two different sets
of replaceable crushing members upon the determination of the control
function. An advantage of this is that the accuracy of the calculation
of the control function becomes greater. An additional advantage,
in particular if one or more measurements are carried out, for example,
every second or every fourth set of replaceable crushing members,
is that the control function will be adapted according to alterations
of the properties over time of the fed-in material.
[0012] Preferably, measured quality parameters from at least three
different occasions are utilized upon the determination of the control
function. By making the measurements on at least three occasions
during the service life of a set of replaceable crushing members,
a considerably safer determination of a control function is obtained.
Even more preferred, the control function should be determined from
values that have been measured on 5 to 10 different occasions during
the service life of a set of crushing members.
[0013] Preferably, each measurement is carried out for at least
three different settings of the crusher setting parameter. At least
three different settings of the crusher setting parameter, and even
more preferred three to five different settings, makes it possible
to obtain also non-linear dependences of the quality parameter and
to take these into consideration upon the determination of the control
function.
[0014] According to a preferred embodiment, if required, the control
function is extrapolated in order to cover the entire time during
which the subsequent set of replaceable crushing members is used.
An advantage of this is that it is not necessary to make a measurement
precisely at the start of operation since the control function may
be extrapolated backward to 0 h of operation. Another advantage
is that the control function may be extrapolated to operation occasions
falling after the last measuring point. An advantage of this is
that the control function works also when a set of crushing members
is utilized longer than the instant of time of operation at which
a last measurement has been made for a preceding set of crushing
members.
[0015] Preferably, said at least one crusher setting parameter
is selected from among: the shortest distance between the first
crusher surface and the second crusher surface, the power generated
by a motor driving the crusher, the quantity of material fed into
the crusher, the rotation speed of a shaft rotating a crushing head
in a gyratory crusher, the horizontal stroke of the lower end of
the shaft in the gyratory crusher, the pressure by which the shaft
in the gyratory crusher loads a setting device that sets the position
of the shaft in the vertical direction, the rotation speed of a
flywheel driving a movable jaw in a jaw crusher, and the horizontal
stroke of the lower end of the movable jaw in a jaw crusher. These
crusher setting parameters all have the advantage that they are
easy to control and that they have a substantial and repeatable
effect on the nature of the crushed material.
[0016] According to an even more preferred embodiment, said at
least one crusher setting parameter comprises a parameter that describes
the shortest distance between the first crusher surface and the
second crusher surface. The smallest distance between the first
and the second crusher surfaces frequently has a very great impact
on the nature of the crushed material. Hence, an adjustment of said
crusher setting parameter, either alone or in combination with the
adjustment of also other crusher setting parameters, is an efficient
way to adjust the effect of the first and second crusher surfaces.
[0017] Conveniently, said at least one quality parameter of the
crushed material is selected from among: grain shape, size distribution,
strength value, quantity of crushed material per time unit, and
quantity of crushed material per energy unit. These measurements
indicate quality parameters having effect on the commercial value
of the crushed material, and which, because of that, there is reason
to optimise according to criteria that may vary from one time to
another. By means of the control function, the method according
to the invention makes it possible to, on any occasion, provide
a crushed product the nature of which gives the highest possible
economical yield.
[0018] According to a preferred embodiment, said given occasion
represents a given operating time, a given quantity of material
having been crushed, or a given quantity of energy having been consumed
in the crushing. These three parameters frequently have a very good
correlation to the wear of the crushing members. Which one of these
three parameters, i.e., operating time, quantity of crushed material,
and consumed energy, gives the best correlation depends on the application
in question and may for each crushing plant be determined from measuring
data.
[0019] An additional object is to provide a crusher, which has
members for such a compensation of the wear in the crusher that
the crushed material always will have predictable properties.
[0020] This object is attained by a crusher according to the preamble,
which crusher is characterized in that the co-operation of the crusher
surfaces is defined by at least one crusher setting parameter, the
crusher having a control device, which is arranged to, by the utilization
of at least one measured quality parameter, which relates to the
nature of the crushed material and which has been measured on at
least two different occasions during the service life of at least
one set of replaceable first and second crushing members and on
each occasion for at least two different settings of the above mentioned
crusher setting parameter, determine a control function that describes
the value of the crusher setting parameter that on a given occasion
gives a crushed material the quality parameter of which is substantially
optimal, and to utilize this control function of the adjustment
of the crusher setting parameter for a subsequent set of replaceable
first and second crushing members in such a way that on a given
occasion for the same subsequent set of replaceable crushing members,
a crushed material can be provided said quality parameter of which
is substantially optimal.
[0021] Another object of the present invention is to provide a
control system for the control of a crusher, which control system
can compensate for the wear that arises in the crusher in such a
way that the crushed material will have predictable properties during
the service life of a pair of crusher surfaces.
[0022] This object is attained by a control system for the control
of a crusher according to the preamble, which control system is
characterized in that it comprises a control device, which is arranged
to, by the utilization of at least one measured quality parameter,
which relates to the nature of the crushed material and which has
been measured on at least two different occasions during the service
life of at least one set of replaceable first and second crushing
members, the co-operation of the crusher surfaces of which is defined
by at least one crusher setting parameter, and on each occasion
for at least two different settings of the above mentioned crusher
setting parameter, determine a control function that describes the
value of the crusher setting parameter that on a given occasion
gives a crushed material the quality parameter of which is substantially
optimal, and to utilize this control function of the adjustment
of the crusher setting parameter for a subsequent set of replaceable
first and second crushing members in such a way that on a given
occasion for the same subsequent set of replaceable crushing members,
a crushed material can be provided said quality parameter of which
is substantially optimal.
[0023] Additional advantages and features of the invention are
evident from the description below and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention will henceforth be described by means of embodiment
examples and reference being made to the accompanying drawings.
[0025] FIG. 1 schematically shows a gyratory crusher having driving
and control devices associated therewith.
[0026] FIG. 2 is a cross-section and shows the Area II, shown in
FIG. 1 in enlargement.
[0027] FIG. 3 is a cross-section and shows the Area III, shown
in FIG. 2 in enlargement.
[0028] FIG. 4 is a cross-section and shows shells, shown in FIGS.
1-3 after the same having been in operation for a period of time.
[0029] FIG. 5 is a cross-section and shows a comparative example
of shells having been in operation for a period of time.
[0030] FIG. 6 is a block diagram that schematically illustrates
an embodiment of a method according to the invention.
[0031] FIG. 7 is a chart and shows a first control function for
use upon the control of a crusher.
[0032] FIG. 8 is a chart and shows a second control function for
use upon the control of a crusher.
[0033] FIG. 9 is a cross-section and shows schematically a jaw
crusher.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] In FIG. 1 a crusher in the form of a gyratory crusher 1
is schematically shown. The crusher 1 has a shaft 1', which at the
lower end 2 thereof is eccentrically mounted. At the upper end thereof,
the shaft 1' carries a crushing head 3. A first, inner, crushing
shell 4 is mounted on the outside of the crushing head 3. In a machine
frame 16 a second, outer, crushing shell 5 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, such as is shown in FIG.
1 along a great part of the extension thereof has a decreasing
width in the downward direction. The shaft 1', and thereby the crushing
head 3 and the inner crushing shell 4 is vertically movable by
means of a hydraulic setting 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 is arranged to bring the shaft 1' and thereby
the crushing head 3 to execute a gyratory motion during operation,
i.e., a motion during which the two crushing shells 4 5 approach
each other along a rotary generatrix and retreat from each other
at a diametrically opposite generatrix. The inner shell 4 and the
outer shell 5 are replaceable and together form a set of replaceable
crushing members.
[0035] 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 10 via an input 13' receives input signals from a
pressure transducer 13 which measures the pressure in the hydraulic
fluid in the setting device 7 8 9 15 and via an input 14' receives
signals from a level 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 power of the motor 10 the hydraulic fluid
pressure in the setting device 7 8 9 15 and thereby also the
position of the shaft 1' in the vertical direction.
[0036] When the crusher 1 is to be calibrated, feeding in of material
is interrupted. The motor 10 continues to be in operation and brings
the crushing head 3 to execute the gyratory pendulum motion. Next,
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 contacts 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 vertical position of the inner shell 4 is recorded by the level
transducer 14 and this position corresponds to a most slender width
of 0 mm of the gap 6. Knowing the gap angle between the inner crushing
shell 4 and the outer crushing shell 5 the width of the gap 6 can
be calculated at any position of the shaft 1' as measured by the
level transducer 14.
[0037] When the calibration is finished, a suitable width of the
gap 6 is set and feeding in of material to the crushing gap 6 of
the crusher 1 is commenced. The fed-in material is crushed a plurality
of times in the gap 6 while it is led downward. Ready-crushed material
then leaves the gap 6 and is transported away.
[0038] FIG. 2 shows more closely the inner crushing shell 4 before
crushing has been commenced, i.e., the shell 4 has not yet been
subjected to any wear. The shell 4 is carried by the crushing head
3 and abuts by a machined support surface 18 against the same. The
shell 4 is locked on the crushing head by a nut 19 as schematically
shown in FIG. 2. The inner shell 4 has a first crushing surface
20 against which material fed in is intended to be crushed. The
outer crushing shell 5 has a support surface 22 which abuts against
the machine frame, not shown in FIG. 2 and a second crushing surface
24. The fed-in material symbolized in FIG. 2 by a substantially
spherical stone block R, will accordingly move downward in a direction
M, which accordingly has a downwardly directed direction component,
while it is crushed a plurality of times between the first crusher
surface 20 and the second crusher surface 24 to smaller and smaller
sizes.
[0039] FIG. 3 shows the shortest distance S between the inner crushing
shell 4 and the outer crushing shell 5. The distance S is usually
present farthest down in the crushing gap 6 i.e., where the crushed
material is just about to leave the crushing gap 6 via an outlet
30. After the material has passed out through the outlet 30 generally
no additional crushing of the material takes place before it leaves
the crusher 1. The distance S, which frequently is called CSS (Closed
Side Setting), has an effect on the properties of the crushed material
leaving the crusher 1. As has been mentioned above, the shaft 1'
executes a gyratory motion and thereby the distance at a certain
point between the inner shell 4 and the outer shell 5 will vary
during the motion of the shaft 1'. The distance S, and CSS, relates
to the absolutely shortest distance between the shells, i.e., when
the inner shell 4 "closes" against the outer shell 5.
The crusher surface 20 of the inner shell 4 has a vertical height
H (see also FIG. 2) that extends from the outlet 30 which corresponds
to a level L1 on the inner shell 4 at which level the distance
to the outer shell 5 usually is shortest, i.e., where the distance
S usually is at hand, to the inlet 32 of the crushing gap 6. The
inlet 32 is the position where material fed in begins to be subjected
to crushing between the inner shell 4 and the outer shell 5. The
inlet 32 corresponds to a level L2 on the inner shell 4 where the
distance to the outer shell 5 usually corresponds to the size of
the largest object that is to be crushed in the crusher 1 at the
shortest distance S in question, i.e., the distance between the
shells at L2 is substantially equal to the diameter of the object
R shown in FIG. 2. The crusher surface 24 of the outer shell 5 has
a vertical height H' (see also FIG. 2) that extends from the outlet
30 which corresponds to a level L1' on the outer shell 5 at which
level the distance to the inner shell 4 usually is shortest, i.e.,
where the distance S is at hand, to the inlet 32 which corresponds
to a level L2' on the outer shell 5 where the distance to the inner
shell 4 is substantially equal to the diameter of the object R shown
in FIG. 2.
[0040] In FIG. 4 an example is shown of what the shells 4 5 shown
in FIGS. 1-3 may look like after having been subjected to wear during
a time of operation of the crusher 1. As can be seen, after the
wear, the inner shell 4 has obtained a crusher surface 120 having
a significantly different geometry than the crusher surface 20 shown
in FIG. 2. The outer shell 5 has obtained a crusher surface 124
having another geometry than the crusher surface 24 shown in FIG.
2. Thereby, between the shells 4 5 a crushing gap 106 is formed
having another shape than the crushing gap 6 shown in FIG. 2. Among
other things, it can be noted that the crushing gap 106 is fairly
wide near the inlet 32 and then, in the downward direction, is
followed by a long narrow portion where the crusher surfaces 120
124 are almost entirely parallel. Immediately before the outlet
30 the crushing gap 106 is widened again before the shortest distance
S is formed on approximately the same location as in the unused
shells. It has now turned out that the crushing gap 106 shown in
FIG. 4 gives a significantly different result as to the quality
parameters of the crushed material than the crushing gap 6 shown
in FIG. 2 even when all crusher setting parameters, including the
distance S, are identical.
[0041] FIG. 5 shows a second example of an inner shell 204 and
an outer shell 205 which shells 204 205 are fastened in a crusher
in the similar way as has been described above. The inner shell
204 has one crusher surface 220 when the shell 204 is new and unworn
and another crusher surface 320 after a time of wear. The outer
shell 205 has one crusher surface 224 when the shell 205 is new
and another crusher surface 324 when it is worn. The consequence
of this is that the geometry of a crushing gap 206 that is formed
between the shells 204 205 depends on whether the shells are new
or if they have been subjected to wear. In the example shown in
FIG. 5 the crushing gap 206 has, after a time of wear, become considerably
widened in the central portion thereof, while near the outlet 30
it has scarcely been altered at all. Thus, on comparison between
FIGS. 2 4 and 5 it can be observed that the geometry of the crushing
gap 6 is altered when the shells 4 5 are worn. How fast and to
what extent the shape of the crushing gap 6 is altered depends among
other things on the size, hardness and shape of the fed-in material,
and the size into which the material is crushed, as well as on the
crusher setting parameters.
[0042] Upon crushing by a gyratory crusher, there are, above all,
three crusher setting parameters that determine the nature of the
crushed material as regards size distribution, grain shape, the
quantity of material that can be crushed in the crusher per time
unit, the strength, etc. These three parameters are CSS (Closed
Side Setting, i.e., the distance S), the rotation speed, i.e., the
number of revolutions per minute that the motor 10 gets the shaft
1' to gyrate, as well as the stroke, i.e., the horizontal distance
that the centre line of the shaft 1' at the lower end 2 thereof
deviates from the centre line of the crusher 1 during the gyratory
motion.
[0043] FIG. 6 schematically shows the way of compensating for wear.
In step 40 a measurement is carried out, for a first set of replaceable
first and second crushing members, of at least one quality parameter,
such as grain size, for at least two different values of a crusher
setting parameter, for instance two different shortest distance
S between shells. In step 42 a second measurement of the quality
parameter is carried out for two different settings of the crusher
setting parameter. Step 40 is carried out on a first occasion, e.g.,
when the crushing members are new, and step 42 is carried out on
a second occasion, e.g., immediately before the first set of crushing
members become entirely worn out and the crushing members are to
be substituted. Conveniently, measurements of the quality parameter
may be carried out on additional occasions during the service life
of the first set of replaceable crushing members. For instance,
if the expected service life of the first set of crushing members
is 1000 h, measurements may be carried out after 0 300 600 and
900 h of operation. After the first set of crushing members has
become worn out, this set is substituted by a subsequent set of
replaceable crushing members. In the step 44 shown in FIG. 6 a
criterion is selected, which defines what is an optimum quality
parameter. The criterion may, for instance, be that the amount of
crushed material in a certain size interval should be maximized.
The crushing by the subsequent set of crushing members is then commenced
in step 46. The step 48 shown in FIG. 6 indicates a possibility
of, at any time during the crushing by the subsequent set of crushing
members, changing criterion of the nature of the material. For instance,
it may instead be chosen to direct the crushing based on a desired
value of another quality parameter, e.g., the grain shape of the
crushed material. In step 50 a control function is determined,
based on the measurements with the first set of crushing members,
of how the crusher setting parameter should be set as a function
of the occasion in question, e.g., current time, in order to meet
the chosen criterion regarding the nature of the material. In step
52 the crusher is adjusted to the setting calculated in step 50.
Conveniently, during the service life of the subsequent second set
of crushing members, in step 54 additional measurements of the
quality parameter may be made in order to improve the basis for
calculation of the control function of subsequent sets of crushing
members, i.e., third set, fourth set and so on. In step 56 which
represents a clock that counts the operating time T during the operation
using the subsequent set of shells, the time T is increased by a
time t, which may be very short, e.g., 0.1 s, before any alteration
of criterion of the nature of the material is possibly made in step
48. If an alteration of criterion has been made in step 48 a new
control function is calculated in step 50 and the crusher is reset
in step 52 according to the new control function. If no alteration
of criterion has been made, in step 52 the crusher is set according
to the value of the crusher setting parameter that has been calculated
from the control function at the operating time T in question.
[0044] Thus, according to FIG. 6 measurements on a first set of
crushing members are utilized for the calculation of the control
function of subsequent, i.e., second, third, fourth, etc., sets
of crushing members. It is appreciated that upon the calculation
of a control function of, for instance, the fourth set of crushing
members, only measurements for the first set, measurements from
the first, second and third set or measurements from only the third
set, may, as an example, be utilized. The choice of which of the
previously made measurements should be utilized for the calculation
of a control function of a subsequent set of crushing members depends
on available measurements, to what extent the properties of the
fed-in material to be crushed are altered over time, etc.
[0045] In Tables 1-3 exemplifying results are schematically shown
from measurement of quality parameters of crushed material on three
occasions. Measurements are carried out with a first set of replaceable
first and second crushing members in the form of an inner shell
4 and an outer shell 5 see FIG. 2 at start (0 h) as well as after
operation for 300 h and 600 h, i.e., on three totally different
occasions. The measurement of quality parameters is carried out
on each occasion for five different settings of the crusher setting
parameter Closed Side Setting (i.e., CSS, which is the same as the
distance S according to FIG. 3), namely 8 9 10 11 and 12 mm.
Remaining crusher setting parameters, among others the horizontal
stroke of the lower end 2 of the shaft 1', the rotation speed of
the shaft 1', the hydraulic pressure in the setting device 7 8
9 15 and the amount of fed-in material per time unit, are kept
constant and are noted so that these settings can be kept in operation
using the subsequent sets of shells 4 5. Upon the measurement,
firstly the distance between the shells 4 5 should be calibrated,
such as has been described above. The two quality parameters that
are measured are the size distribution of the crushed material and
the shape of the grains in a selected fraction, in the example 8-11.2
mm. The size distribution is measured by sieving the crushed material,
the distribution of the material (in % by weight) in four fractions
(0-4 mm, 4-8 mm, 8-11.2 mm and >11.2 mm) being analysed. The
grain shape is analysed by the fact that the crushed material in
the fraction of 8-11.2 mm is analysed in terms of the part of grains
(expressed in % by weight) in this fraction having a length of the
grain of less than three times as large as the thickness of the
grain, also called LT(3) index. In the example shown, it is desirable
that LT(3) is as high as possible.
1TABLE 1 Measurement at start (0 h) Start CSS (mm) 8 9 10 11 12
Size distribution (% by weight): 0-4 mm 55 49 43 40 33 4-8 mm 32
30 28 25 21 8-11.2 mm 12 17 22 23 26 >11.2 mm 1 4 7 12 20 Sum:
100 100 100 100 100 LT(3). 8-11.2 (% by weight): 91.5 92.0 95.0
91.3 90.0
[0046]
2TABLE 2 Measurement after 300 h of operation 300 h CSS (mm) 8
9 10 11 12 Size distribution (% by weight): 0-4 mm 56 51 45 40 34
4-8 mm 33 31 27 25 22 8-11.2 mm 10 15 21 24 26 >11.2 mm 1 3 7
11 18 Sum: 100 100 100 100 100 LT(3), 8-11.2 mm (% by weight) 92.0
94.0 94.0 91.0 89.8
[0047]
3TABLE 3 Measurement after 600 h of operation 600 h CSS (mm) 8
9 10 11 12 Size distribution (% by weight): 0-4 mm 57 52 46 41 34
4-8 mm 34 31 28 26 23 8-11.2 mm 9 14 20 23 26 >11.2 mm 0 3 6
10 17 Sum: 100 100 100 100 100 LT(3), 8-11.2 mm (% by weight) 92.7
93.8 94.3 91.8 90.2
[0048] The data obtained in Tables 1-3 by measurements carried
out for a first set of shells is fed into the control device 11
in order to be utilized in the control of crushing by a second set
of shells that are used for the crushing of a material resembling
the one that was crushed by the first set of shells. FIG. 7 shows
a first example of how such a control may be effected in the form
of a control curve or control function Cl. In this first example,
as a criterion, the operator handling the crusher has selected that
the part of material having a size of 4-11.2 mm shall be maximized,
i.e., that the sum of the part of material in the fraction of 4-8
mm and in the fraction of 8-11.2 mm should be maximized. Thus, in
this case, it is a question about the optimal value of the quality
parameter of size distribution being such that the part of material
in the fraction of 4-11.2 mm should be as great as possible. The
operator enters this criterion into the control device 11. According
to table 1 maximum compliance with the criterion is attained in
new shells, i.e., 0 h of operating time, with CSS=10 mm, i.e., at
a distance S between the shells of 10 mm, 28+22=50% by weight of
the crushed material could be expected to have the desired size
according to Table 1. However, at 300 h, it is for CSS=11 mm where
the greatest part, more precisely 25+24=49% by weight, falls within
the desired interval. At 600 h, 49% by weight is obtained in the
desired size interval for CSS=11 mm as well as for CSS=12 mm. Based
on the criterion of the quality parameter of size distribution given
by the operator and the data found in Tables 1-3 the control device
11 determines a control function C1. This control function C1 states
that CSS should be 10 mm at start, 11 mm at 300 h and 11.5 mm at
600 h. CSS between the given instants of time is calculated by linear
interpolation. Thus, the control function C1 shown in FIG. 7 supplies
the CSS that on any occasion during the service life of a set of
shells could be expected to give the maximum part of material having
the desired size, i.e., 4-11.2 mm. The control device 11 utilizes
the control function C1 shown in FIG. 7 in order to automatically
and during operation set CSS in the crusher 1 for the second set
of shells by means of the setting device 7 8 9 15. Thus, based
on C1 a value of CSS is determined by the control device 11 and
a signal is sent to the setting device 7 8 9 15. As is indicated
in FIG. 7 CSS at 200 h of operation, for instance, will be set
to 10.66 mm by the control device 11. It is also outlined in FIG.
7 that the control function C1 has been extrapolated forward from
600 to 700 h. Such an extrapolation may be carried out in a case
when it is not exactly known at what time the shells 4 5 are worn
out and when there may be a possibility of utilizing the shells
in the second set somewhat longer than the operating time corresponding
to the last measuring point. Analogously, in a case when the first
measuring point corresponds to an operating time of, e.g., 50 h,
an extrapolation backward to 0 h can be carried out when the control
function is to be calculated. Upon a possible extrapolation, it
is important to make it with caution, preferably based on many measurements
and not extending over a long period of time counted from nearest
measurement. It is also convenient not to utilize the compensation
given by the extrapolation to the full extent. If the extrapolated
control function states that CSS should increase linearly from 11.5
mm to 11.7 mm from 600 to 700 h of operating time, it is preferable
to just effect, e.g., 70% of this increase of 0.2 mm, i.e., to increase
CSS from 11.5 to 11.64 mm.
[0049] For allowing CSS, i.e., the shortest distance S between
the shells 4 5 to be directed to the correct value at the respective
instant of time, it is convenient every now and then to make a calibration
so as to ensure that the CSS the control device 11 operates according
to corresponds with reality. It is also possible to utilize the
method described in WO 93/14870 which, based on previous calibrations,
compensates for the wear-dependent alteration of the shortest distance
S between the shells 4 5.
[0050] In FIG. 8 a control curve or control function C2 is illustrated
for a second example where the operator, for a second set of shells,
chooses the criterion to produce the best possible grain shape in
the fraction of 8-11.2 mm, i.e., highest possible LT(3) index in
the fraction of 8-11.2 mm. Hence, in this case, it is a question
of the optimal value of the quality parameter of grain shape being
such that the material in the fraction of 8-11.2 mm should be as
cubic as possible, i.e., that LT(3) index is as high as possible.
From Tables 1-3 the control device 11 can derive that the greatest
LT(3) at 0 h is obtained for CSS 10 mm, at 300 h for CSS 9 mm and
10 mm, and for 600 h at CSS 10 mm. The control function C2 see
FIG. 8 is therefore determined so that CSS should be 10 mm at 0
h, 9.5 mm at 300 h and 10 mm at 600 h, and that a curve fitting
should be made. As is indicated in FIG. 8 CSS at 200 h of operation,
for instance, will be set to 9.60 mm by the control device 11.
[0051] As is seen in the examples described above and illustrated
by means of FIG. 7 and FIG. 8 by the method and the device according
to a preferred embodiment of the invention, it is possible to, based
on measurements of one or more quality parameters of a first set
of shells, automatically set convenient crusher setting parameters
when crushing, with the same or the like material, by a second set
of shells. During the crushing by the second set of shells, additional
measurements are conveniently made that then are utilized, together
with measuring data of the first set of shells, for the calculation
of control functions of a third set of shells and so on.
[0052] It is, as has been mentioned above, possible to change criterion
during operation. For instance, during a period, e.g., 0-300 h,
it is possible to use a criterion of the size distribution and utilize
the control function C1 shown in FIG. 7 and then, e.g., during
a directly following period, e.g., 300-600 h, use a criterion of
the grain shape and utilize the control function C2 shown in FIG.
8. During operation using one set of shells, this makes it possible
to quickly adapt the crushing operation to meet the desired changes
for the nature of the product.
[0053] FIG. 9 schematically shows in section a jaw crusher 401
which is of the rotary crusher type. The jaw crusher 401 has a frame
402 and a jaw 403 movably connected with the same. The jaw 403 carries
a first jaw plate 404 which has a first crusher surface 420. A
second jaw plate 405 which has a second crusher surface 424 is
fastened in the frame 402. At the upper end thereof, the movable
jaw 403 is rotatably fastened on an eccentric shaft 408 on which
at least one flywheel 407 is fastened, which is driven by a motor,
not shown in FIG. 9. Between the first jaw plate 404 and the second
jaw plate 405 a crushing gap 406 is formed, which in section, as
is shown in FIG. 9 has a width decreasing in the downward direction.
When the motor rotates the flywheel 407 the same will get the upper
part of the movable jaw 403 to describe an ellipse and the first
jaw plate 404 will thereby alternately move towards and away from
the second jaw plate 405. When the jaw plates 404 405 are new,
the crusher surfaces 420 424 thereof are, as seen in cross-section,
substantially planar in the example shown in FIG. 9 (the crusher
surfaces 420 424 may, however, also be provided with different
types of patterns that, for instance, increase the gripping power).
Fed-in material, in FIG. 9 symbolized by a substantially spherical
stone block R, will accordingly move from an inlet 432 downward
in a direction M, which accordingly has a downwardly directed direction
component, while it is crushed successively between the first crusher
surface 420 and the second crusher surface 424 to smaller and smaller
sizes. The crushed material leaves the crusher 401 via an outlet
430. Normally a shortest distance S is present between the crusher
surfaces 420 424 at the outlet 430. The distance between the crusher
surfaces 420 424 can be adjusted since the position of a so-called
joint flap 415 which is jointed in the frame 402 and in the lower
part of the jaw 403 is adjustable, for instance, by means of a
hydraulic cylinder 409. After a time of operation, the jaw plates
404 405 will be worn down and crusher surfaces 520 524 will obtain
another geometry than the original and also affecting the geometry
and function of the crushing gap 406. In analogy with what has been
described above for a gyratory crusher, for a first set of jaw plates
404 405 it is possible to carry out measurements of at least one
quality parameter, e.g., size distribution or grain shape of crushed
material, for at least two different settings of a crusher setting
parameter, e.g., two different shortest distances S between the
plates 404 405 two different rotation speeds of the flywheel 407
or two different horizontal strokes of the lower end of the movable
jaw 403 which strokes can be adjusted by altering the angle of
inclination of the joint flap 415 e.g., by displacing the fixing
point of the hydraulic cylinder 409 in the frame 402. The measurements
of the quality parameter for the two settings are repeated on at
least two different occasions. A control function may then be calculated
and, with the purpose of compensating for the alteration of the
crushing gap 406 upon wear, be utilized for the setting of the crusher
401 during operation when a subsequent set of jaw plates have been
mounted therein.
[0054] It will be appreciated that a great number of modifications
of the embodiments and examples described above are feasible within
the scope of the invention, such as it is defined by the accompanying
claims.
[0055] For instance, more accurate methods of calculation, such
as various regression methods, may be utilized in order to calculate
a more accurate control function from measurement results, like
those in Tables 1-3 above, regarding quality parameters, and thereby
a more accurate value of the crusher setting parameter that on a
certain occasion gives the best possible compliance with the chosen
criterion.
[0056] Above, simple criteria are exemplified, i.e., control functions
relating to a single quality parameter that is to be optimized.
Naturally, more complex control functions may be utilized, which
for instance specify that two or more quality parameters, e.g.,
size distribution and grain shape, should be optimized simultaneously
under certain conditions. For instance, a control function may be
produced that has the object of maximising the amount of material
in a certain size interval but that this maximization is limited
by the grain shape simultaneously not being allowed to be below
a certain value. Likewise, from measurements for a set of crushing
members, it is of course possible to calculate a control function
that for any occasion describes the setting of a plurality of crusher
setting parameters, e.g., values of both the shortest distance S
and of the amount of fed-in material, provided that a plurality
of crusher setting parameters have been varied during the measurement.
Apart from the above-mentioned quality parameters of size distribution
and grain shape, it is also possible to use other quality parameters
for the control of the crusher. Examples of such quality parameters
are strength values, such as for instance abrasive resistance measured
according to, for instance, European Standard A 1097-1 and disintegration
resistance measured according to, for instance, European Standard
A 1097-2 which are measurements of the mechanical strength of the
crushed material. Additional examples of quality parameters are
the amount of crushed material per time unit and the amount of crushed
material per energy unit, which quality parameters accordingly are
measurements of the efficiency by which the crushed product has
been produced and thereby also describe the nature of the material.
[0057] The fact that the crusher setting parameter is to be set
to such a value that the quality parameter of the crushed material
becomes substantially optimal does not necessarily mean that the
value of the quality parameter always should be maximized. The fact
that the quality parameter is optimal may also mean that, e.g.,
a grain shape is not below a certain minimum value or is within
a desired interval.
[0058] Above, it is described how measurements from a first set
of crushing members are utilized upon the calculation of the control
function of the subsequent sets of crushing members, i.e., of second,
third, etc., sets of crushing members. It is preferable also, for
these second, third, etc., sets of crushing members, to carry out
measurements and to utilize these measurements upon the determination
of control functions of crushing members subsequent to these sets
of crushing members. The additional measurements carried out have
two advantages. One advantage is that the accuracy of the calculation
of the control function becomes greater the more measurements it
could be based on. Another advantage is that time-dependent alterations
of the properties of the fed-in material, e.g., hardness, size distribution,
will have an impact in the measurements. For this reason, upon the
calculation of a control function of a set of crushing members,
it is preferred to give most consideration to those measurements
having been made for the closest preceding sets of crushing members
and less, or no, consideration to those measurements having been
made a relatively long time ago, when the fed-in material possibly
had somewhat different properties.
[0059] According to the above, it is described how measurements
are carried out on three occasions during the service life of a
first set of crushing members. It is of course also possible, although
less preferred, to carry out only two measurements during the service
life of the first set of crushing members. It is, as an alternative,
also possible to carry out one measurement during the service life
of a first set of crushing members, e.g., after 100 h of operation
using this first set of crushing members, and one measurement during
the service life of a second set of crushing members, e.g., after
700 h of operation using this second set of crushing members, and
to utilize these two measurements for the determination of a control
function that is utilized for the adjustment of a crusher setting
parameter upon crushing by a subsequent, third, set of crushing
members.
[0060] In the examples above, it is described how measurements
are carried out on a plurality of occasions, which correspond to
a certain number of hours of operation, i.e., the measurements are
made at certain instants of time. In certain cases, wear of the
crusher surfaces is more correlated to how many tons of material
have been crushed between the crusher surfaces, or how much energy
the crusher surfaces have transferred to the material, than to the
time the crusher surfaces have been in operation. Therefore, occasionally
it is instead desirable to relate the occasions when measurements
should be carried out to a certain number of tons of crushed material,
a certain amount of energy consumed in the driving device of the
crusher, or some other parameter correlating to the wear. In such
a case, the x-axis in FIGS. 7 and 8 will not be graduated in unit
of hours but instead, for instance, in unit of tons or in unit of
kWh, and the control function being used for the setting of the
crusher setting parameter for a subsequent set of replaceable crushing
members will instead relate to the current, accumulated, amount
of crushed material starting from the subsequent set, or the current,
accumulated, consumed energy starting from the subsequent set, instead
of to the current, accumulated, time. Thus, the control system could,
for instance, measure the accumulated quantity of crushed material
for the subsequent set of replaceable crushing members and when,
for instance, 5000 t of material have been crushed, derive from
a control function, that for instance may be based on measurements
at 0 7000 and 14000 t of crushed material by a preceding set, which
setting of the crusher setting parameter that on this occasion,
i.e., at 5000 t of crushed material, gives the best compliance with
the quality parameter according to the chosen criterion.
[0061] As is seen from the above, the control device 11 conveniently
automatically sets the correct value of the crusher setting parameter,
based on a control function C1. However, an alternative solution
is that the control device 11 on a display, a pointer instrument
or the like, presents the value calculated from C1 of the crusher
setting parameter, and that an operator manually adjusts this value
of the crusher.
[0062] It is appreciated that the invention also may be applied
to other types of crushers than those described above. For instance,
a gyratory crusher having a hydraulic control of the vertical position
of the inner shell is described above. The invention may also be
applied to, among other things, crushers that have a mechanical
setting of the gap between the inner and outer shell, for instance
the type of crushers that is described in U.S. Pat. No. 1894601
in the name of Symons. In the last-mentioned type of crushers, occasionally
called Symons type, the setting of the gap between the inner and
outer shell is carried out by a case, in which the outer shell is
fastened, being threaded in a machine frame and turned in relation
to the same for the achievement of the desired gap. The invention
may also be applied to other types of jaw crushers than the one
described above, e.g., jaw crushers of the pendulum crusher type.
[0063] While the present invention has been described with respect
to particular preferred embodiments of the present invention, this
is by way of illustration for purposes of disclosure rather than
to confine the invention to any specific arrangement as there are
various alterations, changes, deviations, eliminations, substitutions,
omissions and departures which may be made in the particular embodiments
shown and described without departing from the scope of the present
invention as defined only by a proper interpretation of the appended
claims. |