Abstrict Malfunctions of sliding bearings of cone crushers used in crushing
stone are anticipated by providing sensors in connection to bearing
parts, by means of which sensors it is possible to observe increases
in friction forces. A beginning bearing damage can be detected by
means of sensors at such an early stage, that extensive damage to
bearings and to other parts of the crusher can be prevented.
Claims What is claimed is:
1. A method for monitoring the condition of bearings in a cone
or a gyratory crusher and for decreasing damage caused by a deteriorated
bearing wherein friction force between bearing surfaces in a crusher
is monitored by a sensor, and information gained from the monitoring
of the friction force carried out by the sensor is used in an alerting
or control system of the crusher.
2. A method in accordance with claim 1 wherein the friction force
between bearing surfaces of the crusher is monitored by a sensor
selected from the group consisting of a piezoelectric sensor, a
force sensor, a mechanical sensor, a hydraulic sensor or a strain-gauge
transducer.
3. A method in accordance with claim 1 wherein the friction force
between bearing surfaces is monitored by a sensor integrated in
an adjusting piston guide.
4. A method in accordance with claim 1 wherein a signal from one
or more sensors is analyzed and by comparing it to reference material
previously stored in a control system information is gained about
which bearing surface is being damaged.
5. A method in accordance with claim 2 wherein the friction force
between bearing surfaces is monitored by a sensor integrated in
an adjusting piston guide.
6. A method in accordance with claim 2 wherein a signal from one
or more sensors is analyzed and by comparing it to reference material
previously stored in a control system information is gained about
which bearing surface is being damaged.
7. A method in accordance with claim 3 wherein a signal from one
or more sensors is analyzed and by comparing it to reference material
previously stored in a control system information is gained about
which bearing surface is being damaged.
8. A method in accordance with claim 5 wherein a signal from one
or more sensors is analyzed and by comparing it to reference material
previously stored in a control system information is gained about
which bearing surface is being damaged.
9. A cone crusher comprising at least one sensor, which provides
an output signal indicating a friction force between bearing surfaces
of the crusher.
10. A crusher in accordance with claim 9 wherein the crusher is
a gyratory crusher.
11. A crusher in accordance with claim 9 wherein the sensor is
selected from the group consisting of a piezoelectric sensor, a
force sensor, a mechanical sensor, a hydraulic sensor or a strain-gauge
transducer.
12. A crusher in accordance with claim 9 wherein the sensor is
integrated in an adjusting piston guide.
13. A crusher in accordance with claim 10 wherein the sensor is
selected from the group consisting of a piezoelectric sensor, a
force sensor a mechanical sensor, a hydraulic sensor or a strain-gauge
transducer.
14. A crusher in accordance with claim 10 wherein the sensor is
integrated in an adjusting piston guide.
15. A crusher in accordance with claim 11 wherein the sensor is
integrated in an adjusting piston guide.
16. A crusher in accordance with claim 13 wherein the sensor is
integrated in an adjusting piston guide.
Description TECHNICAL FIELD
This invention relates to cone and gyratory crushers. More specifically,
the invention relates to the monitoring of sliding bearings of a
cone or gyratory crusher so, that an incipient bearing failure can
be detected at such an early stage, that extensive damage to bearings
and to other parts of the crusher can be prevented.
BACKGROUND ART
In cone crushers there is a perpendicular eccentric shaft and in
that shaft an oblique inner bore. In the bore is fitted a main shaft,
to which shaft a crushing head is usually attached. The head is
laterally surrounded by the crusher frame, to which frame is attached
a concave, functioning as a wear part. To the head is correspondingly
attached a mantle, functioning as a wear part. The mantle and the
concave together form a crushing cavity, and within this, feed material
is crushed. When the eccentric shaft is rotated, the main shaft
together with the head is forced into an oscillating movement, whereby
the gap between the mantle and the concave varies at each location
during the work cycle. The smallest gap during a work cycle is called
the crusher setting, and the difference between maximum gap and
minimum gap is called the crusher stroke. By means of the crusher
setting and the crusher stroke, e.g. the particle size distribution
of produced crushed stone and the production capacity of the crusher
can be controlled.
The main shaft of a crusher is often supported in the crusher frame
by a top bearing at its upper end. This subtype of cone crusher
is usually referred to as a gyratory crusher.
A gyratory crusher is usually adjustable by a hydraulic system
thus, that the main shaft can be moved vertically relative to the
crusher frame. This makes possible a change of the setting so, that
the particle size of crushed stone will conform to the required
size, and/or keeping the setting constant during wearing of the
wear parts.
In other types of cone crushers, the adjustment can be made also
by raising and lowering the upper crusher frame and the concave
attached to it relative to the lower crusher frame and to the main
shaft, which remains vertically stationary relative to the lower
frame.
In a crusher there are many surfaces associated by sliding bearings.
Depending on the type of crusher these include, for example, surfaces
between: main shaft and eccentric shaft eccentric shaft and lower
frame eccentric shaft and adjusting piston main shaft and upper
frame main shaft and adjusting piston
The above-mentioned members are not usually in immediate contact
with each other, but in practice there are usually one or more bearing
sleeves between them, so the actual bearing surfaces usually form
between the above-mentioned members and these bearings.
When the bearings of a crusher work properly, friction forces between
the crusher bearing surfaces are minimal. If a crusher is affected
by a disturbance in lubrication, the friction forces between bearing
surfaces will increase and the bearings will be in danger of seizure.
This kind of disturbances can be, for example, crusher overload,
contaminants in lubricating oil, or pressure or flow decrease of
lubricating oil.
Seizure damage has a tendency to advance in a crusher from one
bearing surface to another. Lets assume, for example, that there
is a disturbance in the lubrication between the main shaft and the
eccentric shaft of a crusher and the mentioned bearing surfaces
start to seize. This causes heating of the eccentric shaft. When
the heat is conducted to the bearing surface between the eccentric
shaft and the crusher frame, the lubrication of this bearing surface
can also be impaired, which causes also this bearing surface to
start to seize.
The seizure described in this example can also advance in the opposite
direction from one bearing surface to another, or it can also advance
between other bearing surfaces.
The case described as an example can lead also to a situation,
where the bearings of a crusher along with the main parts of a crusher,
such as the frame, the main shaft, the eccentric shaft etc. are
completely damaged. Repair costs of this kind of total damage are
difficult to estimate, because the costs differ greatly from case
to case depending on, for example, the crusher type. On an average,
the costs may be about between EUR 20 000-50 000 (at year 2000 prices).
In addition, the stoppage of a crusher causes considerable costs.
In Finnish patent 100554 a method is disclosed for monitoring
the condition of crusher bearings by monitoring the rotation speed
of a main shaft around its axis. When the gap of a crusher is full
of stones, these stones will decrease the rotation speed of the
head and the main shaft. Thus, a relatively large increase in friction
between the main shaft and the eccentric shaft is necessary before
a change in the rotation speed of the main shaft can be detected.
At this point, the damage at the sliding surface between the eccentric
shaft and the main shaft has already advanced relatively far.
DETAILED DESCRIPTION OF THE INVENTION
General Description
If an increase of friction forces at the bearing surfaces of a
crusher can be detected early enough, it will give an indication
of a beginning seizure. Then it is possible to create a procedure
to inform the crusher operator about the disturbance. In its simplest
form, such an alarm system can be, for example, a light or sound
signal. It is also possible to connect the mentioned indication
to the control system for the crusher or the whole crushing process
thus, that the initial failure will control the crusher or the crushing
process in order to keep the damage as small as possible. The indication
can be arranged, for example, to: open the overpressure valve of
the crusher, which will cause the crusher setting to increase quickly
and the bearing load to decrease disengage the crusher power transmission
coupling, which will cause the crusher to stop and the bearing load
to decrease stop the crusher drive motor, which will cause the crusher
to stop and the bearing load to decrease shorten the stroke of the
crusher, which will cause the bearing load to decrease stop the
crusher feeder, which will decrease the load of the crusher and
the bearings when the crusher becomes empty.
When a beginning seizure can be detected early, the damage cannot
advance from one bearing surface to another. It is sufficient to
change detachably fitted bearing sleeves or other similar bearing
members and to grind the corresponding surface on the major crusher
parts. Repair costs are then only about 10-20% of the repair costs
caused by total damage. Also the production losses of a crushing
plant will decrease because of shorter stoppage. If damage is detected
early enough and the damage remains minimal, it is in certain circumstances
even possible to postpone repair of the damage to a normal maintenance
break.
DETAILED DESCRIPTION
The invention is described in detail in the following with references
to the enclosed drawings, wherein
FIGS. 1 and 2 represent typical gyratory crushers in accordance
with the state of the art,
FIG. 3 represents a typical cone crusher in accordance with the
state of the art,
FIG. 4 is an enlarged cross-section bottom view of a detail from
the crusher of FIG. 1 also showing forces appearing in bearings
and their behavior,
FIG. 5a is an enlarged representation of an embodiment of the invention
applied in the bottom section of the crusher of FIG. 1
FIG. 5b is an enlarged representation of an embodiment of the invention
applied in the top section of the crusher of FIG. 1
FIG. 6a is an enlarged representation of an embodiment of the invention
applied in a bottom section of the crusher shown in FIG. 2
FIG. 6b is an enlarged representation of an embodiment of the invention
applied in a top section of the crusher shown in FIG. 2 and
FIG. 7 is an enlarged representation of an embodiment of the invention
applied in the crusher shown in FIG. 3.
The main parts of the crusher shown in FIG. 1 are lower frame 1
upper frame 2 main shaft 3 head 4 concave 5 mantle 6 crushing
cavity 7 transmission 8 eccentric shaft 9 adjusting piston 10
adjusting piston guide 11 axial bearing 12 of the eccentric shaft,
radial bearing 13 of the eccentric shaft, axial bearing 14 15
16 of the main shaft, radial bearing 17 of the main shaft, main
shaft protecting sleeve 18 and support bearing 19.
The crusher frame consists of two main units: lower frame 1 and
upper frame 2. The concave 5 attached to the upper frame and the
mantle 6 attached by means of head 4 to the main shaft 3 forms the
crushing cavity 7 into which material to be crushed will be fed
from top of the crusher.
Transmission 8 by means of which the eccentric shaft 9 is rotated,
is mounted in the lower frame. In the eccentric shaft there is a
bore at slanted angle in relation to the crusher central axis, into
which bore the main shaft is fitted. When the transmission rotates
the eccentric shaft inside the crusher frame, it causes an oscillating
movement in the main shaft fitted in the bore in the eccentric shaft.
The crusher setting is adjusted by pumping hydraulic medium into
a space between the adjusting piston 10 and the lower frame. In
this application, the adjusting piston of the crusher is shaped
as a cylinder, open at its upper end and closed at its bottom end,
and the hem of the adjusting piston fits between the lower frame
of the crusher and the eccentric shaft.
Between the main shaft and the eccentric shaft is the radial bearing
17 of the main shaft, which bearing conveys radial forces affecting
the main shaft to the crusher frame. Between the eccentric shaft
and the adjusting piston is the radial bearing 13 of the eccentric
shaft, carrying out the same task. The axial bearing 12 of the eccentric
shaft conveys axial forces between the eccentric shaft and the lower
frame.
In the outer surface of the adjusting piston there is a groove,
into which is fitted the adjusting piston guide 11 attached to
the lower frame of the crusher. The task of the guide is to prevent
rotation of the adjusting piston inside the frame of the crusher
due to friction forces in the radial bearing of the eccentric shaft
and the axial bearing of the main shaft. The prevention of rotation
is important, because in this way a sufficiently high relative speed
is achieved in parts moving in respect to each other, so that a
lubrication film will form.
Axial forces of the main shaft are conveyed to the crusher frame
through pressurized hydraulic medium and the axial bearing 14 15
16 of the main shaft. In this application the axial bearing consists
of three separate parts, whereby at least two of those parts have
counter-surfaces which are part of a spherical surface.
Radial forces of the main shaft are conveyed to the upper frame
of the crusher through the support bearing 19. Usually, a main shaft
protection sleeve is provided in crushers to protect the main shaft
from the wearing effect of the material to be crushed.
The same main crusher parts shown in FIG. 1 appear in the crusher
shown in FIG. 2. The crusher setting is adjusted by pumping hydraulic
medium into a space between the adjusting piston 10 and the lower
frame. In this application, the adjusting piston is located wholly
below the main shaft, and it does not function as a member conveying
radial forces of the main shaft to the lower frame of the crusher.
The main parts of the crusher shown in FIG. 3 are frame 20 bowl
21 main shaft 3 head 4 concave 5 mantle 6 crushing cavity 7
transmission 8 eccentric shaft 9 adjusting motor 22 adjustment
ring 23 axial bearing 12 of the eccentric shaft, radial bearing
13 of the head, axial bearing 24 25 26 of the head, and radial
bearing 17 of the main shaft. The concave 5 attached to bowl 21
and mantle 6 attached to head 4 form the crushing cavity 7 into
which material to be crushed will be fed from top of the crusher.
In the lower frame is placed transmission 8 by means of which
the eccentric shaft 9 is rotated. In the eccentric shaft, there
is a bore, into which main shaft 3 which is fixed to the frame
of the crusher, is fitted. When the transmission rotates the eccentric
shaft around the main shaft, it brings the head, which is connected
at the main shaft through bearings, into an oscillating movement.
The setting of the crusher is adjusted by rotating the bowl 21
with the adjusting motor 22 which will cause the bowl to rise or
lower itself along the threads of the adjustment ring 23.
Between the main shaft and the eccentric shaft there is the radial
bearing 17 of the main shaft, which bearing conveys radial forces
of the head to the crusher frame. Between the eccentric shaft and
the head there is the head radial bearing 13 having the same function.
The axial bearing 12 of the eccentric shaft conveys axial forces
between the eccentric shaft and the frame of the crusher.
Axial forces of the head are conveyed to the frame of the crusher
through head axial bearing 24 25 26. In this application, the
axial bearing consists of three separate parts, at least two of
those parts having counterpart surfaces, which are part of a spherical
surface.
Radial forces of the head are conveyed through the radial bearing
17 of the main shaft to the main shaft and further to the frame
of the crusher.
FIG. 4 represents a horizontal cross-section of a lower part of
the crusher shown in FIG. 1. The main parts shown are lower frame
1 main shaft 3 eccentric shaft 9 adjusting piston guide 11 radial
bearing 13 of the eccentric shaft, and radial bearing 17 of the
main shaft.
The figure also shows the following forces appearing in a crusher:
a radial component F.sub.L of a force acting on the frame of the
crusher from the main shaft while material is being crushed
a friction force F.sub..mu.1 caused by the force F.sub.L at the
surface between the main shaft and the radial bearing of the main
shaft
a friction force F.sub..mu.2 caused by the force F.sub.L at the
surface between the eccentric shaft and the radial bearing of the
eccentric shaft
a torque M caused by the friction forces F.sub..mu.1 and F.sub..mu.2
and acting on the adjusting piston
a reaction force F, created by the adjusting piston guide and opposing
the torque M, which force F prevents the adjusting piston from revolving.
From the main shaft is conveyed the force F.sub.L, which causes
friction forces F.sub..mu.1 and F.sub..mu.2 of which the first
is a friction force between the main shaft and the radial bearing
of the main shaft, and the second is a friction force between the
eccentric shaft and the radial bearing of the eccentric shaft. In
a normal lubrication situation, the friction coefficient is very
small, for example 0001 which causes the friction force to be
also very small.
If the lubrication situation deteriorates, the friction coefficient
will increase dramatically and with it the friction force, for example
10 . . . 100 times. Bearing friction causes the torque M at the
adjusting piston, which torque is countered by the support reaction
F of the adjusting piston guide. By measuring the force F or its
effects, information about bearing friction forces can be attained.
By simultaneously observing the power used by the crusher, the crusher
setting, and the control pressure of the crusher, a fair apprehension
of the load situations of different bearings can be gained. If the
load and lubrication situation of the bearings turns critical, the
damage can be prevented or minimized by controlling the crusher
or the material feed, for example by decreasing or halting the input
of feed material, by enlarging the crusher setting, by stopping
the crusher, or by giving the crusher operator an alert, based on
which the operator decides what actions should be taken to eliminate
the problem.
In FIG. 5a is represented the lower part of a crusher which is
of the type shown in FIG. 1 and which includes, among other things,
an eccentric shaft 9 an adjusting piston 10 an axial bearing 12
of the eccentric shaft, a radial bearing 13 of the eccentric shaft,
an axial bearing 14 15 16 of the main shaft, and a radial bearing
17 of the main shaft as well as sensors 27 and 28. In a crusher
in accordance with FIG. 5a, the reaction force of the torque caused
by sensor 27 and affecting the adjusting piston 10 is observed by
sensor 27. If the sensor detects an increase in the reaction force,
it is a sign of a beginning damage at radial bearing 13 of the eccentric
shaft, or the axial bearing 17 of the main shaft. The sensor is
fitted in the adjusting piston guide 11. The reaction force of a
torque caused by the eccentric shaft and acting on the axial bearing
12 of the eccentric shaft is observed by sensor 28. If the sensor
detects an increase in the reaction force, it is a sign of beginning
damage at the axial bearing of the eccentric shaft.
In FIG. 5b is represented the upper part of a crusher which is
of the same type as the one shown in FIG. 1 and which includes
among other things a main shaft 3 a support bearing 19 and a sensor
29. In a crusher in accordance with FIG. 5b, the reaction force
of a torque caused by sensor 29 and affecting the support bearing
is observed by sensor 29. If the sensor detects an increase in the
reaction force, it is a sign of beginning damage at the support
bearing.
In crushers equipped in accordance with FIGS. 5a and 5b can, for
example, the shape of the following bearing surfaces be controlled
by sensors:
bearing surfaces of the axial bearing combination 14 15 16
eccentric shaft 9--axial bearing 12 of the eccentric shaft
eccentric shaft 9--radial bearing 13 of the eccentric shaft
main shaft 3--support(top) bearing 19.
FIG. 6a represents the lower part of a crusher of the same type
as the one shown in FIG. 2 and in accordance with the present invention,
and which includes, among others, a main shaft 3 an eccentric shaft
9 an adjusting piston 10 an axial bearing 12 of the eccentric
shaft, a radial bearing 13 of the eccentric shaft, an axial bearing
14 15 16 of the main shaft, a radial bearing 17 of the main shaft,
and sensors 29 and 30. In FIG. 6b is similarly represented the upper
part of a crusher in accordance with the present invention, which
includes among others a main shaft 3 a support bearing 31 32
and a sensor 33.
In a crusher in accordance with FIG. 6a, the reaction force of
a torque caused by sensor 29 and directed at the radial bearing
of the eccentric shaft, is monitored by means of sensor 29. If the
sensor detects an increase in the reaction force, it is a sign of
a beginning damage in the radial bearing of the eccentric shaft.
By means of sensor 30 a reaction force of a torque, caused by the
sensor and directed at the adjusting piston, is monitored. If the
sensor detects an increase in the reaction force, it is a sign of
a beginning damage in the axial bearing of the main shaft.
In a crusher in accordance with FIG. 6b, the reaction force of
a torque caused by sensor 33 and directed at the support bearing
31 32 is monitored by means of sensor 33. If the sensor detects
an increase in the reaction force, it is a sign of a beginning damage
in the support bearing.
In a crusher in accordance with FIG. 2 and equipped in accordance
with FIG. 6 the following bearing surfaces, for example, can be
monitored by sensors:
the bearing surfaces of a bearing combination 14 15 16 of the
main shaft,
eccentric shaft 9--axial bearing 12 of the eccentric shaft,
eccentric shaft 9--radial bearing 13 of the eccentric shaft,
bearing surfaces 3 26 27 2 between the support bearing combination,
the frame, and the main shaft.
FIG. 7 is a representation of the middle part of a crusher in accordance
with FIG. 3 and equipped with sensors placed in accordance with
the present invention. The figure shows, among others, main shaft
3 head 4 eccentric shaft 9 axial bearing 12 of the eccentric
shaft, radial bearing 13 of the head, axial bearing 24 25 26 of
the head, radial bearing 17 of the main shaft, and sensors 34 35
36 and 37.
In a crusher in accordance with the FIG. 7 the reaction force
of a torque caused by sensor 34 and acting on the axial bearing
of the eccentric shaft is monitored by sensor 34. If the sensor
detects an increase in the reaction force, it is a sign of a beginning
damage in the axial bearing of the eccentric shaft. By means of
sensor 35 the reaction force of a torque caused by the head and
aimed at the axial bearing of the head, is monitored. If the sensor
detects an increase in the reaction force, it is a sign of a beginning
damage in the axial bearing of the head. By means of sensor 36
the reaction force of a torque caused by the main shaft and acting
on the radial bearing of the main shaft, is monitored. If the sensor
detects an increase in the reaction force, it is a sign of a beginning
damage in the radial bearing of the main shaft. By means of sensor
37 the reaction force of a torque caused by the sensor and acting
on the radial bearing of the head is monitored. If the sensor detects
an increase in the reaction force, it is a sign of a beginning damage
in the radial bearing of the head.
The sensors 36 and 37 are not in a fixed position with respect
to the crusher, but sensor 36 moves with the eccentric shaft and
sensor 37 moves with the head. Therefore, the transfer of the sensor
signal from the sensor to the outside of the crusher requires special
arrangements. However, this function can be accomplished with a
slip ring or with a transmitter connected to the sensor and a receiver
located outside of the crusher.
In a crusher in accordance with FIG. 7 for example, the following
bearing surfaces can be monitored by sensors:
the bearing surfaces of the axial bearing combination 24 25 of
the head,
the bearing surfaces between the frame 20 and the eccentric shaft
9
main shaft 3--radial bearing 17 of the main shaft,
eccentric shaft 9--radial bearing 13 of the head.
The present invention is not restricted to any particular sensor
technology. Monitoring the condition of a bearing can be based not
only on measuring a force, but also on measuring a dislocation or,
for example, on measurement of a surface pressure. In addition to
a force, a bending moment can also be measured as well as a distortion
caused by it. Therefore, for example, a piezoelectric sensor, a
force sensor, a mechanical sensor, a pressure sensor or a strain-gauge
transducer can be used as a sensor.
From the point of view of the invention, it is insignificant in
which manner the sensor indicates damage: the indication can be
transferred mechanically, hydraulically or electrically. Monitoring
can be based not only on the direct monitoring of a bearing, but
also on indirect monitoring, through some other part.
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