Abstrict A gyratory crusher includes a first shell-having a support surface
intended to abut against a shell-carrying member, and a first crushing
surface intended to be brought into contact with material fed into
the upper portion of the crusher, to crush the material against
a corresponding second crushing surface disposed on a second shell
arranged opposite the first shell. The first and second crushing
surfaces oppose one another in spaced relationship to form a gap
through which the material travels as it is being crushed. The gap
includes an upper inlet and a lower outlet. Over at least 50% of
the vertical height, from the outlet upwards toward the inlet, the
first crushing surface is machined to a run-out tolerance, which
on each level along the machined part of the vertical height does
not exceed one thousandth of the largest diameter of the first crushing
surface, or 0.5 mm, whichever is less.
Claims What is claimed is:
1. A shell for use in a gyratory crusher, the shell including at
least one support surface and a crushing surface, the crushing surface
defining a largest diameter and having an inlet and an outlet, the
inlet disposed above the outlet, the crushing surface having a vertical
height extending from the outlet to the inlet, the crushing surface
being machined to a run-out tolerance along at least 50% of the
vertical height from the outlet upwards, wherein the run-out tolerance
around a circumference of the machined crushing surface does not
exceed one-thousandth of the largest diameter, or 0.5 mm, whichever
is less.
2. The shell according to claim 1 wherein the maximum value does
not exceed 0.35 mm.
3. The shell according to claim 2 wherein the crushing surface
is machined to the run-out tolerance along at least 75% of the vertical
height.
4. The shell according to claim 1 wherein the maximum value does
not exceed 0.35 mm.
5. The shell according to claim 1 wherein the crushing surface
is machined to the run-out tolerance along substantially the entire
vertical height.
6. A method of providing a shell for use in a gyratory crusher,
the shell including an inlet and an outlet, the inlet disposed above
the outlet, the shell including at least one support surface and
a crushing surface, the crushing surface defining a largest diameter,
the crushing surface having a vertical height extending from the
outlet to the inlet, the method comprising machining the crushing
surface to a run-out tolerance along at least 50% of the vertical
height from the outlet upwards, wherein the run-out tolerance around
a circumference of the machined crushing surface does not exceed
one-thousandth of the largest diameter, or 0.5 mm, whichever is
less.
7. The method according to claim 6 wherein the machining step comprises
a turning operation.
8. The method according to claim 6 wherein the crushing surface
is machined along substantially the entire vertical height.
9. The method according to claim 8 wherein the machining step has
a machining allowance of at least 2 mm.
10. The method according to claim 9 wherein the machining allowance
is 2-8 mm.
11. A gyratory crusher comprising: a first shell-carrying member;
a first shell having at least one support surface abutting against
the first shell-carrying member, and a first crushing surface; a
second shell having at least one support surface abutting against
the second shell-carrying member, and a second crushing surface;
the first and second crushing surfaces opposing one another and
defining therebetween a gap in which material is to be crushed,
the gap having an inlet and an outlet, the inlet disposed above
the outlet, the first crushing surface defining a largest diameter
and having a vertical height extending from the outlet to the inlet,
the first crushing surface being machined to a run-out tolerance
along at least 50% of the vertical height from the outlet upwards,
wherein the run-out tolerance around a circumference of the machined
crushing surface does not exceed one-thousandth of the largest diameter,
or 0.5 mm, whichever is less.
12. The gyratory crusher according to claim 11 wherein the first
shell comprises an inner shell and the second shell comprises an
outer shell, the second crushing surface defining a largest diameter
and having a vertical height extending from the outlet to the inlet,
the second crushing surface being machined to a run-out tolerance
along at least 50% of the vertical height of the second crushing
surface from the outlet upwards, wherein the run-out tolerance around
a circumference of the machined second crushing surface does not
exceed one-thousandth of the largest diameter of the second crushing
surface, or 0.5 mm, whichever is less.
13. The gyratory crusher according to claim 12 wherein a sum of
the run-out tolerances of opposing portions of the first and second
crushing surfaces is no greater than 0.7 mm.
14. The gyratory crusher according to claim 11 wherein the largest
diameter of each of the first and second crushing surfaces is at
least 500 mm.
Description [0001] The present application claims priority under 35 U.S.C.
.sctn. 119 to patent application Ser. No. 0302974-1 filed in Sweden
on Nov. 12 2004 the content of which is hereby incorporated by
reference.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to a shell for use in a gyratory
crusher, which shell has at least one support surface, which is
intended to abut against a shell-carrying member, and a first crushing
surface, which is intended to be brought into contact with a material
that is supplied at the upper portion of the crusher and is to be
crushed, and to crush said material in a crushing gap against a
corresponding second crushing surface on a second shell complementary
with the shell.
[0003] The present invention also relates to a method of producing
a shell for use in a gyratory crusher, which shell is of the above-mentioned
kind.
[0004] The invention also relates to a gyratory crusher, which,
on one hand, has a first shell, which has at least one support surface,
which is intended to abut against a first shell-carrying member,
and a first crushing surface, and on the other hand a second shell,
which has at least one support surface, which is intended to abut
against a second shell-carrying member, and a second crushing surface,
the first crushing surface and the second crushing surface being
arranged to be brought into contact with a material supplied at
the upper portion of the crusher, which material is to be crushed
in a crushing gap between the crushing surfaces.
BACKGROUND ART
[0005] Upon fine crushing of hard material, e.g. stone blocks or
ore blocks, material is crushed that has an initial size of approx.
100 mm or less to a size of typically approx. 0-25 mm. Fine crushing
is frequently carried out by means of a gyratory crusher. An example
of a gyratory crusher is disclosed in U.S. Pat. No. 4566638. Said
crusher has an outer shell that is mounted in a stand. An inner
shell is fastened on a crushing head. The inner and outer shells
are usually cast in manganese steel, which is strain hardening,
i.e., the steel gets an increased hardness when it is exposed to
mechanical action. The crushing head is fastened on a shaft, which
at the lower end thereof is eccentrically mounted and which is driven
by a motor. Between the outer and the inner shell, a crushing gap
is formed into which material can be supplied. Upon crushing, the
motor will get the shaft and thereby the crushing head to execute
a gyratory pendulum motion, i.e., a motion during which the inner
and the outer shell approach each other along a rotary generatrix
and retreat from each other along another diametrically opposite
generatrix.
[0006] WO 93/14870 discloses a method to set the gap between the
inner and the outer shell in a gyratory crusher. Upon a calibration,
a crushing head, on which the inner shell is mounted, is moved vertically
upward until the inner shell comes into contact with the outer shell.
This contact, which is used as a reference upon setting of the width
of the gap between the inner and the outer shell, occurs at a point
where the gap is most slender. In order to avoid the possibility
that cast remainders or other protruding objects can affect the
calibration, cast shells are subjected to a machining before they
are used. This machining means that the part of the shell that can
be expected to contact an opposite shell during the calibration,
is made even.
[0007] It is a problem upon fine crushing of hard material by means
of a gyratory crusher that a great share of the crushed material
has a larger size than what was intended. For this reason, a great
part of the crushed material has to be crushed one more time for
achievement of the desired size.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide a shell
for use upon fine crushing in a gyratory crusher, which shell decreases
or entirely eliminates the problems of the known technique.
[0009] This object is provided by means of a shell, which is of
the kind mentioned by way of introduction and is characterized in
that the first crushing surface has a vertical height that extends
upward from the outlet of the crushing gap along the first crushing
surface to the inlet of the crushing gap, the first crushing surface
over at least 50% of said vertical height, from the outlet and upward
along the first crushing surface, having been machined to a run-out
tolerance, which on each level along the machined part of the vertical
height of the first crushing surface is maximum one thousandth of
the largest diameter of the first crushing surface, however maximum
0.5 mm.
[0010] It has turned out that by means of a shell of this type,
the material that is supplied to a crusher, in which the shell has
been mounted, can be crushed to considerably smaller sizes. This
entails an increased efficiency in the crushing since less energy
is consumed for the achievement of a certain quantity of crushed
material having a certain size. The mechanical load on the crusher
will also become considerable less. For the achievement of this
increased efficiency, at least 50% of the vertical height of the
crushing surface according to the above has to be machined to small
run-out tolerance. Namely, it has turned out that the compression
of the material that is to be crushed gives rise to a pressure,
which is very great up to said level on the crushing surface. Therefore,
a larger run-out in the crushing surface somewhere along said 50%
of the vertical height of the crushing surface would entail a substantially
increased mechanical load and that the material cannot be crushed
to equally small sizes. Upon machining of, for instance, only 10%
of the height of the crushing surface, i.e., only in the area of
the shortest distance between the inner and the outer shell, it
is true that it is possible to set an exact gap between the shells
but no increase of efficiency is obtained. The interesting measure
in the invention is the run-out tolerance, which is to be viewed
as a measure of roundness in combination with centring. A crushing
surface that has high roundness but is not centred will not entail
any increased efficiency. The machined part of the crushing surface
has to be machined to a very small run-out tolerance in order to
provide the increased efficiency and the decreased mechanical load.
Thus, the run-out must not anywhere along the machined part of the
crushing surface exceed 0.5 mm.
[0011] According to a preferred embodiment, said run-out tolerance
is maximum 0.35 mm. Closed Side Setting (CSS) is the shortest distance
between the inner shell and the outer shell and is the shortest
distance between the inner and the outer shell that arises during
the gyrating motion, more precisely when the inner shell "closes"
against the outer shell. A very small run-out tolerance is especially
advantageous when very small shortest distances (CSS) between the
inner and the outer shell are utilized, for instance, when the shortest
distance is approx. 4 to 8 mm. A very small run-out tolerance, such
as maximum 0.35 mm, makes it possible to provide a more slender
gap than what previously has been possible without the mechanical
load during the crushing becoming too great. Even more preferred,
the run-out tolerance should be maximum 0.5 thousandths of the largest
diameter of the first crushing surface, however maximum 0.25 mm.
[0012] Preferably, the first crushing surface has been machined
to said run-out tolerance over at least 75% of the vertical height
thereof from the outlet. This entails the advantage that in particular
shells intended for crushing of fine material, for instance crushing
of stones having an initial size of 5-30 mm, can be utilized efficiently
and without too great mechanical load on the crusher. Thus, it is
possible to hold a small shortest distance (CSS) between the inner
and the outer shell and thereby provide a crushing to small sizes.
At such a small shortest distance between the shells, the compression,
and thereby the pressure, will become great also up to a level of
approx. 75% of the vertical height of the crushing surfaces from
the outlet, but the same means, thanks to the run-out tolerance
being small up to at least the same level, no problem. Even more
preferred is that the first crushing surface has been machined to
the run-out tolerance over substantially the entire vertical height
thereof. With such a crushing surface, which has been machined to
small run-out tolerance over up to 100% of the vertical height thereof,
the shell becomes robust to supplied material and can be used both
for crushing of fine-grained material at a very small shortest distance
(CSS), such as 3-6 mm, but also for crushing of a somewhat larger
material at a larger shortest distance (CSS), such as 6-20 mm.
[0013] Another object of the present invention is to provide an
efficient method of manufacturing a shell for use upon fine crushing
in a gyratory crusher, which shell decreases or entirely eliminates
the problems of the known technique.
[0014] This object is provided by a method, which is of the above-mentioned
kind and is characterized in that first-mentioned shell is produced
by a shell work piece being manufactured and provided with the first
crushing surface, which is given a vertical height that extends
upward from the outlet of the crushing gap along the first crushing
surface to the inlet of the crushing gap, the first crushing surface
over at least 50% of said vertical height, from the outlet and upward
along the first crushing surface, being provided with a machining
allowance, that a surface on the shell work piece is machined in
order to form said support surface, and that said first crushing
surface along said at least 50% of said vertical height is machined
to a run-out tolerance that on each level along the machined part
of the vertical height of the first crushing surface is maximum
one thousandth of the largest diameter of the first crushing surface,
however maximum 0.5 mm. An advantage of the machining allowance
is that material can be removed from the entire crushing surface
upon the machining, also at such portions where the manufacture,
for instance casting with subsequent heat treatment, has given rise
to geometrical deformations.
[0015] According to a preferred embodiment, the first crushing
surface is machined by being turned. Turning is an efficient machining
method for achievement of a small run-out tolerance. The fact that
the shell is rotated during the machining substantially facilitates
the possibility of achieving a very small run-out tolerance. An
additional advantage is that a certain strain hardening of the crushing
surface is provided upon turning. A common material in crushing
shells is manganese steel, which has the property that it is strain
hardening. Thereby, upon the turning of a shell of manganese steel,
a certain increase of hardness is provided in the crushing surface,
which may be an advantage in cases when the shell should be used
for crushing of material, which is wearing but not particularly
hard and therefore cannot generate a strain hardening fast in the
crushing surface.
[0016] Preferably, in the manufacture of the shell work piece,
substantially the entire first crushing surface is provided with
a machining allowance of at least 2 mm, substantially the entire
first crushing surface being machined to said run-out tolerance
of the first crushing surface. According to an even more preferred
embodiment, the machining allowance should be 2-8 mm. The machining
allowance has to be at least so large that no geometrical deformations
remain in the machined part of the crushing surface after machining
to a small run-out tolerance. A machining allowance of at least
2 mm, more preferred at least 3 mm, means that conventional casting
can be utilized in the production of a shell work piece. The machining
allowance should not be larger than approx. 8 mm, even more preferred
approx. 6 mm, since this means increased material and machining
costs.
[0017] It is also an object of the present invention to provide
a gyratory crusher for use upon fine crushing, which gyratory crusher
is more efficient than the known crushers.
[0018] This object is provided by a gyratory crusher, which is
of the above-mentioned kind and is characterized in that the first
crushing surface has a vertical height that extends upward from
the outlet of the crushing gap along the first crushing surface
to the inlet of the crushing gap, the first crushing surface over
at least 50% of said vertical height, from the outlet and upward
along the first crushing surface, having been machined to a run-out
tolerance, which on each level along the machined part of the vertical
height of the first crushing surface is maximum one thousandth of
the largest diameter of the first crushing surface, however maximum
0.5 mm. A gyratory crusher of this type will enable crushing at
very small shortest distances (CSS) between the shells, which ensures
an efficient crushing to small sizes.
[0019] According to a preferred embodiment, the first shell is
an inner shell and the second shell an outer shell, the second crushing
surface having a second vertical height that extends upward from
the outlet along the second crushing surface to the inlet, the second
crushing surface over at least 50% of said second vertical height,
from the outlet and upward along the second crushing surface, having
been machined to a run-out tolerance, which on each level along
the machined part of the second vertical height of the second crushing
surface is maximum one thousandth of the largest diameter of the
second crushing surface, however maximum 0.5 mm. When both the inner
and the outer shell has a crushing surface which along at least
50% of the respective vertical height thereof has been machined
to a small run-out tolerance, the crusher will be able to operate
at very small shortest distances (CSS) between the inner and the
outer shell and thereby provide a large size reduction of the supplied
material.
[0020] According to an even more preferred embodiment, the sum
of the run-out tolerances of the first crushing surface and the
second crushing surface on each level along mutually opposite portions
of the machined parts of the crushing surfaces is maximum 0.7 mm.
This sum of run-out tolerances, which accordingly is calculated
as the sum of the run-out tolerance of the first crushing surface
and the run-out tolerance of the second crushing surface on each
level on the mutually opposite portions where the two crushing surfaces
are machined to small run-out tolerances, will ensure a considerably
lower mechanical load from fatigue point of view. An additional
advantage is that the crushing surface that is most easy to machine,
e.g. the crushing surface of the inner shell, can be machined to
a very small run-out tolerance, e.g. maximum 0.2 mm, the second
crushing surface, e.g. the crushing surface of the outer shell,
can be machined to a relatively seen larger run-out tolerance, e.g.
maximum 0.4 mm.
[0021] Preferably, the respective crushing surfaces of the first
and the second shell have a largest diameter of at least 500 mm.
It is only at larger sizes on the inner and the outer shell that
said run-out tolerance gives the increased efficiency in the form
of increased quantity of crushed material and/or smaller size on
the crushed material and better grain shape on the crushed material
and that the decreased mechanical load on the crusher may lead to
a significant increase of the service life of the crusher.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will henceforth be described by means of embodiment
examples and with reference to the appended drawings.
[0023] FIG. 1 schematically shows a gyratory crusher having associated
driving, setting and control devices.
[0024] FIG. 2 is a cross-section and shows the area II shown in
FIG. 1 in enlargement.
[0025] FIG. 3 is a cross-section and shows the area III shown in
FIG. 2 in enlargement.
[0026] FIG. 4 is a cross-section and shows a second embodiment
of the invention.
[0027] FIG. 5 is a cross-section and shows a device for the manufacture
of shells according to the present invention.
[0028] FIG. 6 is a cross-section and shows measurement of the run-out
on a crushing surface.
[0029] FIG. 7 is a graph and shows size distribution of supplied
material and crushed product in two tests.
[0030] FIG. 8 is a graph and shows variations of pressure in a
test of crushing.
[0031] FIG. 9 is a graph and shows variations of pressure in a
comparative test of crushing.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] In FIG. 1 a gyratory crusher 1 is schematically shown,
which is of the type production crusher for fine crushing and is
intended for the greatest feasible production of crushed material
of a certain desired size. With fine crushing, here it is meant
that the crusher is intended to crush material that has an original
size of less than 100 mm to a size of less than 20 mm. By production
crusher, here is meant a crusher that is intended to produce more
than approx. 10 tons/hour (t/h) of crushed material and that the
crushing surfaces of the crusher, described below, have a largest
diameter that is larger than 500 mm. 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, as
is shown in FIG. 1 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.
[0033] In operation, the crusher is controlled by a control device
11 which: (a) via an input 12' receives input signals from a transducer
12 arranged at the motor 10 which transducer measures the load
on the motor, (b) 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 (c) 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, whereby the device 11 controls, on the
basis of received input signals, among other things, the hydraulic
fluid pressure in the setting device 7 8 9 15.
[0034] When the crusher 1 is to be calibrated, the supply 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 registered 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.
[0035] When the calibration is finished, a suitable width of the
gap 6 is set and the supply of material to the crushing gap 6 of
the crusher 1 is commenced. The supplied material is crushed in
the gap 6 and can then be collected vertically below the same.
[0036] FIG. 2 shows the inner crushing shell 4 which is carried
by the crushing head 3 and is locked on the same by a nut 19 schematically
shown in FIG. 2. A machined support surface 18 on the inner crushing
shell 4 abuts against the crushing head 3. The inner shell 4 has
a first crushing surface 20 against which supplied material 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 supplied material, in FIG.
2 symbolized by a substantially spherical stone block R, will accordingly
move downward in the direction M while it is crushed between the
first crushing surface 20 and the second crushing surface 24 to
decreasingly smaller sizes.
[0037] FIG. 3 shows the shortest distance S1 between the inner
crushing shell 4 and the outer crushing shell 5. The distance S1
usually exists farthest down in the crusher 1 i.e., where the crushed
material just is 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 S1 which frequently is called CSS (closed
side setting), decides the size of the crushed material leaving
the crusher 1. As has been mentioned above, the shaft 1' executes
a gyrating motion and thereby the distance at a given point between
the inner shell 4 and the outer shell 5 will vary during the motion
of the shaft 1'. The distance S1 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 crushing 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 S1 usually is at
hand, to the inlet 32 of the crushing gap 6. The inlet 32 is the
position where supplied material begins to be exposed 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 a distance S2 to the outer
shell 5 usually corresponds to the size of the largest object which
is to be crushed in the crusher 1 at the shortest distance S1 in
question, i.e., the distance S2 is substantially equal to the diameter
of the object R shown in FIG. 2. The crushing 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 S1 is at hand, to the inlet
32 which corresponds to a level L2' on the outer shell 5 where
usually the above-mentioned distance S2 is at hand, i.e., where
the distance to the inner shell 4 is substantially equal to the
diameter of the object R shown in FIG. 2.
[0038] The inner shell 4 and the outer shell 5 that are shown in
FIGS. 1-3 are so-called M shells that are intended for crushing
stone blocks R having an original size of typically approx. 50-100
mm to a size of typically approx. 10-20 mm. Upon such crushing,
a shortest distance S1 i.e., CSS, of approx. 10-20 mm is used.
The crushing surface 20 of the inner shell 4 has along the entire
vertical height H thereof been turned to a run-out tolerance that
is less than 0.5 mm. Also, the crushing surface 24 of the outer
shell 5 has been machined to a run-out tolerance of less than 0.5
mm over the entire vertical height H' thereof.
[0039] FIG. 4 shows an alternative embodiment of the present invention.
In FIG. 4 an inner shell 104 and an outer shell 105 are shown,
which are of the so-called EF type, which means that they are intended
for extreme fine crushing. The inner shell 104 has a support surface
118 which abuts against the crushing head 3 and a crushing surface
120. The crushing surface 120 has a vertical height H, which extends
upward from an outlet 130 of a crushing gap 106 which corresponds
to a level L1 which usually is situated at the shortest distance
S1 between the inner shell 104 and the outer shell 105 to the inlet
132 of the crushing gap 106 which corresponds to a level L2 which
usually is situated where the distance S2 to the outer shell 105
substantially corresponds to the size of a largest object R1 that
is to be crushed. In analogy with what has been described above,
the outer shell 105 has a support surface 122 and a crushing surface
124. The crushing surface 124 has a vertical height H', which extends
upward from the outlet 130 to the inlet 132 i.e., from the level
L1' to the level L2'. Thus, between the crushing surfaces 120 124
the proper crushing gap 106 is formed, where crushing of supplied
stone blocks R1 is carried out. As is clearly seen in FIG. 4 the
inner shell 104 has a portion 126 that is located above the level
L2 and the outer shell 105 has a portion 128 that is located above
the level L2'. Between said portions 126 128 an antechamber 129
is formed that serves as store of material that awaits being dosed
into between the crushing surfaces 120 124. No proper crushing
takes place in the chamber 129 and the portions 126 128 do therefore
not constitute any part of the crushing surfaces 120 124 which
end on the respective level L2 L2', i.e., at the inlet 132.
[0040] It may be convenient to machine the shell 105 to a small
run-out tolerance also a distance above the level L2'. The reason
is that the level for the inlet 132 after a time of operation will
be moved upward on the shell 105 since the shells 104 105 then
have become worn and the shell 104 as a consequence of this has
had to be moved upward for retention of a constant, smallest distance
S1.
[0041] The shells 104 105 shown in FIG. 4 are intended for crushing
small objects, i.e., objects R1 that have an original size of typically
approx. 10-50 mm to a size of typically approx. 0-12 mm. Upon such
crushing, a shortest distance S1 i.e., CSS, of approx. 2-10 mm
is used. The crushing surface 120 of the inner shell 104 has along
the entire vertical height H thereof been turned to a run-out tolerance
that is maximum 0.35. Also, the crushing surface 124 of the outer
shell 105 has over the entire vertical height H' thereof been machined
to a run-out tolerance of maximum 0.35 mm.
[0042] The manufacture of shells 4 5 104 105 proceeds in the
following way.
[0043] In a first step, a shell work piece is manufactured, for
instance by casting in a sand mould. The first step resembles the
already known ways to manufacture shell work pieces by, for instance,
casting, with the essential difference that the shell work piece
is manufactured having a machining allowance of approx. 3-6 mm all
over the portion of the shell work piece that in the finished shell
should constitute the crushing surface. Also the part of the shell
work piece that in the finished shell should constitute the support
surface is provided with a machining allowance. After cooling, the
shell work piece is taken out of the mould and is heat-treated.
[0044] In a second step, the thus-formed shell work piece 34 is
fastened, as is seen in FIG. 5 in a vertical boring mill 36. The
vertical boring mill 36 has a rotary plate 38 and a number of clamping
jaws 40 by means of which the position of the shell work piece 34
on the plate 38 can be set in such a way that the centre line of
the shell work piece 34 generally coincides with the centre line
42 of the plate 38. The plate 38 is then caused to rotate the shell
work piece 34. A turning tool C1 is utilized in order to machine
a support surface 18 on the inside of the shell work piece 34. The
machining is made in such a way that the support surface 18 gets
a small tolerance in respect of roundness. Thanks to the fact that
the shell work piece 34 is rotated during the machining, the support
surface 18 will furthermore become centred around the centre axis
of the shell work piece and thereby obtain a small run-out tolerance.
[0045] In a third step, a turning tool C2 is utilized in order
to machine a crushing surface 20 in the shell work piece 34 while
the same is rotated in the vertical boring mill 36. The third step
is commenced directly after the machining of the support surface
18 without the shell work piece 34 first having been released from
the plate 38. Thanks to the fact that the shell work piece 34 is
rotated during the machining, it becomes relatively easy to machine
a crushing surface 20 having a small run-out tolerance. As is indicated
by arrows at the turning tool C2 the entire crushing surface 20
is machined to said run-out tolerance by the machining allowance,
symbolized by W, being worked away. By means of this method of production,
the crushing surface 20 will obtain a small run-out tolerance in
relation to the support surface 18. When the finished shell 4 is
placed on a crushing head 3 the crushing surface 20 will, thanks
to the fact that it has a small run-out tolerance in relation to
the support surface 18 obtain a small run-out tolerance also in
the mounted state.
[0046] It will be appreciated that it is also possible to reverse
the second and third steps, i.e., in a second step, to machine the
crushing surface 20 and in a third step, without the shell work
piece 34 first being released from the plate 38 machine the support
surface 18. Alternatively, it is also possible to work up both the
crushing surface 20 and the support surface 18 simultaneously in
the same working step. In all cases, it applies that the crushing
surface 20 and the support surface 18 both are machined to low run-out
tolerance and furthermore to have a common centre line.
[0047] It will be appreciated that an outer shell can be produced
in a similar way as has been described above, reference having been
made to an inner shell.
[0048] After completion of the machining thereof, the shell is
then checked in respect of run-out tolerance. In FIG. 6 it is shown
how such a control can be carried out according to the Swedish Standard
SS 2650 method 20.1.6 (Run-out in conical surface) by means of
a so-called dial test indicator. As is seen in FIG. 6 a shell 104
i.e., the type of shell that is described in connection with FIG.
4 has been mounted on the plate 38 of the vertical boring mill
36. It will be appreciated that a check of the run-out tolerance
conveniently can be carried out directly after the crushing surface
120 has been worked up but before the shell 104 has been dismounted
from the plate 38. A possible resetting of the run-out tolerance
can be carried out in direct conjunction with the check. The run-out
tolerance over at least 50% of the height of the crushing surface,
counted from the outlet 130 and upward, should be maximum one thousandth
of the largest diameter D of the crushing surface 120 as is seen
in FIG. 6 however maximum 0.5 mm in absolute numbers.
[0049] It will be appreciated that a number of modifications of
the above-described embodiments are feasible within the scope of
the present invention.
[0050] Thus, it is also possible to machine only a part of the
crushing surface to a small run-out tolerance. However, at least
50% of the vertical height of the crushing surface, counted from
the outlet 30 i.e., from the first level L1 L1', has to be machined
to this run-out tolerance. This is exemplified in FIG. 2 by a vertical
height H50 which describes the height of the smallest area of the
crushing surface 20 that has to be machined to a small run-out tolerance.
Preferably, at least 75% of the vertical height of the crushing
surface, from the outlet 30 i.e., from the first level L1 L1',
should be machined to a small run-out tolerance, which in FIG. 2
is exemplified by a vertical height H75. In all cases, it applies
that the run-out tolerance within the entire machined area, which
accordingly is the area that lies within the height H50 or a greater
height, e.g. H75 or H, should be machined in such a way that the
run-out tolerance on a arbitrary level within this area meets the
established requirements.
[0051] The above-described machining of the crushing surface to
a small run-out tolerance may also be carried out in other ways
than turning. For instance, the surface may be ground. Turning is,
however, preferred since it is a relatively easy way to provide
a small run-out tolerance.
[0052] In the description above, a crusher is described that has
a hydraulic setting of the vertical position of the inner shell.
It will be appreciated that the invention also can be applied to,
among other things, crushers that have a mechanical setting of the
gap between the inner and the outer shell, for instance, the type
of crushers that is disclosed in Symons U.S. Pat. No. 1894601.
In the last-mentioned type of crushers, occasionally called Symons
type, the setting of the gap between the inner and the outer shell
is carried out by the fact that a case, in which the outer shell
is fastened, is threaded in a machine frame and is turned in relation
to the same for the achievement of the desired gap. These crushers
are frequently even more sensible to mechanical load than the above-described
crushers having hydraulic setting device and may therefore derive
great advantage from the present invention.
[0053] In the description above it is described that each shell
4 5 has one support surface 18 22 each. The invention may also
be applied to a shell that has two or more support surfaces.
[0054] In the description above it is mentioned that the shortest
distance S1 (CSS) between the inner shell 4 and the outer shell
5 usually exists at the outlet 30 of the crushing gap 6 i.e., at
the level L1 and L1', respectively. However, there is also a case
where the shortest distance S1 exists a bit above the outlet 30
i.e., above the level L1 and L1', respectively. In such cases, it
is frequently convenient to machine the respective crushing surface
20 24 from the outlet 30 i.e., from the level L1 and L1', respectively,
and upward to at least 75% of the respective crushing surface's
20 24 vertical height from the outlet 30.
[0055] The present invention may be applied to all sizes of crushers.
The invention is especially advantageous in production crushers,
which are crushers the shells of which have crushing surfaces having
a largest diameter D of 500 mm and larger, which crushers are intended
for a rate of production of approx. 10 tons/hour of crushed material
or more during continuous operation. The invention is particularly
advantageous in production crushers intended for fine crushing,
i.e., when objects having an initial size of approx. 100 mm or smaller
is to be crushed to a size of approx. 20 mm or smaller. In particular
upon crushing of material to a size of approx. 10 mm or smaller
and when the shortest distance S1 (CSS) between the inner and the
outer shell is approx. 15 mm or shorter, the present invention will
ensure a considerable energy-saving and reduced mechanical load
in comparison with the known technique.
EXAMPLES
[0056] In order to illustrate the advantages of the present invention,
two tests were carried out. In test 1 an outer shell and an inner
shell were used, the crushing surfaces of which had been machined
to a small run-out tolerance according to the invention. In test
2 an inner shell and an outer shell according to prior art were
used.
[0057] Test 1
[0058] The test was carried out with a gyratory crusher of the
type H3800 which is marketed by Sandvik SRP AB, Svedala, SE. A
shell work piece of the type EF, i.e., the type of shell 104 that
is shown in FIG. 4 was machined in a lathe to a small run-out tolerance
all over the crushing surface 120. The crushing surface 120 of the
inner shell 104 had a largest diameter D of 950 mm, which diameter
was located at the level L1. After turning, the run-out of the shell
104 was measured by means of a dial test indicator. In one way,
which corresponds to the way indicated in FIG. 6 the measurement
of run-out was made perpendicularly to the respective surface on
six levels A to F, which levels were evenly distributed along the
vertical height H of the crushing surface 120 in relation to the
support surface 118 which constituted a reference. The level F
substantially corresponded to the outlet 130 i.e., the level L1
and the level A substantially corresponded to the inlet 132 i.e.,
the level L2. On each level A-F, the run-out was measured in eight
turning positions, i.e., in eight points or sectors (in table 1
below denominated sectors 1-8), evenly distributed around the circumference
of the level in question. Thus, the sector 1 in each level served
as a reference point, so the position of the dial test indicator
is represented as "0" in table 1 below. As the indicator
progressed from sector no. 1 to the next sector no. 2 around the
circumference of a respective level, if the diameter of the crushing
surface did not change, then the indicator would not move and a
"0" reading would result. However, if the diameter changed,
then the indicator would be moved in or out from the reference position,
depending on whether the diameter increased or decreased. In one
direction of movement of the indicator, the measured distance of
movement would be given a positive value (+), and in the opposite
direction of movement, it would be given a negative value (-). The
largest difference between the measured deviations of the eight
sectors at a given level would constitute the largest run-out for
that level. Thus, if the largest positive deviation were +4 and
the largest negative deviation on the same level were -6 then the
largest run-out for that level would be 4-(-6)=10. In table 1 the
measured run-out of the inner shell is seen in hundredths of mm:
1TABLE 1 Measured absolute values of run-outs at inner shell according
to the invention [in units of 1/100 mm] Sector 1 2 3 4 5 6 7 8 Level
A 0 <1 <1 <1 <1 <1 <1 <1 B 0 <1 <1 <1
<1 <1 <1 <1 C 0 <1 <1 <1 <1 <1 <1
<1 D 0 <1 <1 <1 <1 <1 <1 <1 E 0 <1 <1
<1 <1 <1 <1 <1 F 0 <1 <1 <1 <1 <1
<1 <1
[0059] By <1 is meant that the run-out is greater than -0.01
mm and less than +0.01 mm. Accordingly, the highest possible run-out
at any level is the difference between the maximum and minimum possible
values, i.e., 0.01-(-0.01)=0.02 mm. Thus, on each level the crushing
surface 120 has a run-out tolerance that is better than 0.5 mm.
Hence, the ratio of the largest run-out to the largest diameter
of the shell was 0.02 mm/950 mm.times.1000=0.021 thousandths, i.e.,
the largest run-out was smaller than 0.021 thousandths of the largest
diameter D of the crushing surface 120.
[0060] An outer shell, which was of the type of the outer shell
105 (called EF) shown in FIG. 4 was machined in a vertical boring
mill. After the machining, which was carried out all over the crushing
surface 124 the run-out on the corresponding levels A to F (where
the level F substantially corresponded to the outlet 130 and the
level A substantially corresponded to the inlet 132) was measured
in eight sectors per level in analogy with what has been described
above for the inner shell. Table 2 shows the measured run-outs for
the outer shell 105:
2TABLE 2 Measured run-out at outer shell according to the invention
[1/100 mm] Sector 1 2 3 4 5 6 7 8 Level A 0 -19 -30 -22 -8 15 23
21 B 0 -19 -30 -21 -9 11 18 17 C 0 12 -19 -12 -5 5 9 10 D 0 -6 -10
-6 -5 -2 -3 2 E 0 -7 -7 -5 -5 -9 -9 -4 F 0 -8 -4 -5 -4 -14 -12 -9
[0061] As is seen in table 2 the largest run-out, i.e., the largest
difference between the measured values on a certain level, was 0.53
mm (i.e., 23-(-30)/100 mm), more precisely on a level A, i.e., at
the inlet 132. The first 50% of the vertical height H' of the crushing
surface 124 counted from the outlet 130 i.e., the level L1', and
upward corresponds to the levels F to D in table 2. The largest
run-out within said levels F to D is 0-(-14)/100 mm=0.14 mm, more
precisely on a level F. Thus, on each level along 50% of the vertical
height H' of the crushing surface 124 counted upward from the outlet
130 the outer shell 105 has a run-out tolerance which is better
than 0.5 mm. The crushing surface 124 of the outer shell 105 had
a largest diameter of 1000 mm, which diameter was at hand at the
level L1'. The ratio of the largest run-out along 50% of the vertical
height H' of the crushing surface 124 counted from the outlet 130
to the largest diameter of the shell was 0.14 mm/1000 mm.times.1000=0.14
thousandths, i.e., the largest run-out was 0.14 thousandths of the
largest diameter D of the crushing surface 124. Hence, the sum of
the run-out of the first crushing surface 120 and the run-out of
the second crushing surface 124 was not on any level, along the
first 50% of the respective crushing surface's vertical height H
and H', respectively, from the outlet 130 larger than 0.02 mm+0.14
mm=0.16 mm.
[0062] The inner and the outer shell 104 105 were then mounted
in a crusher, which beforehand had been adjusted so that the machine
frame 16 as well as the crushing head 3 had a run-out tolerance
that was smaller than 0.05 mm.
[0063] In test 1 a material called "16-22 mm" was introduced
in the crusher. The grain size distribution in the supplied material
as well as in the crushed product of test 1 is seen in FIG. 7 which
shows the amounts of the supplied material and of the product passing
through a sieve as a function of the sieve aperture size. The crusher
was set to operate at an average pressure in the hydraulic fluid
in the setting device of the crusher of approx. 5 MPa. Upon the
crushing, between the inner and the outer shell a shortest distance
S1 i.e., CSS, of 4.0 mm was held. The crusher consumed a power
of approx. 135 kW. The total amount of material that was crushed
was 48 t/h. Of the crushed product, 74.6% by weight had a size that
was smaller than 4 mm, accordingly the production of material having
a size smaller than 4 mm being 48 t/h.times.74.6% by weight=35.8
Vh. The grain shape of the crushed material was evaluated by means
of a so-called LT index. LT designates that the ratio of the length
of a grain to the width thereof is smaller than 3. Thus, the LT
index states the weight share of grain having a ratio of length
to thickness that is smaller than 3. Normally, LT index should be
as high as possible, since it means that the material has a high
cubicity, which is desirable in most crushing applications. The
crushed material in test 1 had an LT index of 93% by weight in the
fraction 5-8 mm. FIG. 8 shows the pressure variation in the hydraulic
fluid as a function of time. The average pressure in the hydraulic
fluid of the setting device was approx. 5.19 MPa and the standard
deviation was 0.61 MPa.
[0064] Test 2
[0065] With the purpose of comparing the invention with prior art,
a test 2 was carried out in which an inner and an outer shell according
to prior art were mounted in the crusher used in test 1. The shells
were of the type EF, i.e., they were of the same type as those that
were used in test 1. The shells that were used in test 2 were, however,
of known type and thereby not machined to a small run-out tolerance.
Before the test was started, the run-out of the inner shell and
the outer shell was measured by means of the above-described method.
The run-out of the inner shell according to prior art is seen in
table 3.
3TABLE 3 Measured run-out at inner shell according to prior art
[1/100 mm] Sector 1 2 3 4 5 6 7 8 Level A 0 38 -11 -13 14 13 -13
56 B 0 72 -46 -113 1 66 -4 9 C 0 28 -68 -172 -55 3 -65 34 D 0 -13
-115 -175 -128 -79 -70 -18 E 0 -12 -27 -54 -78 -82 -50 -18 F 0 -12
-28 -65 -82 -88 -52 -19
[0066] As is seen in table 3 the largest run-out of the crushing
surface, i.e., the largest difference between the measured values
on a certain level, was 2.06 mm (i.e., 34-(-172)/100 mm), more precisely
on level C. The largest run-out along 50% of the vertical height
of the crushing surface, counted from the outlet of the crushing
gap and upward, was 1.75 mm, more precisely on level D.
[0067] The run-out of the outer shell according to prior art is
seen in table 4.
4TABLE 4 Measured run-out at outer shell according to prior art
[1/100 mm] Sector 1 2 3 4 5 6 7 8 Level A 0 -110 -194 -194 -360
-193 -23 23 B 0 -99 -176 -176 -314 -197 -11 14 C 0 -23 -72 -172
-238 -133 48 14 D 0 -1 -21 -104 -205 -103 21 2 E 0 -20 -45 -82 -90
-102 -109 -53 F 0 -33 -54 -99 -91 -120 -125 -68
[0068] As is seen in table 4 the largest run-out, i.e., the largest
difference between the measured values on a certain level, was 3.83
mm (i.e., 23-(-360)/100 mm), more precisely on level A, i.e., at
the inlet of the crushing gap. The largest run-out along 50% of
the vertical height of the crushing surface, counted from the outlet
of the crushing gap and upward, was 2.26 mm, more precisely on level
D.
[0069] In test 2 a material called "16-22 mm" was introduced
in the crusher. The grain size distribution in the supplied material
as well as in the crushed product of test 2 are seen in FIG. 7.
As is seen in FIG. 7 the supplied material had almost identical
grain size distribution in test 1 and test 2. The crusher was set
to operate at an average pressure in the hydraulic fluid in the
setting device of the crusher of approx. 5 MPa. Upon the crushing,
a shortest distance S1 was held between the inner and the outer
shell, i.e., CSS, of 5.8 mm. The crusher consumed a power of approx.
150 kW. The amount of material that was crushed was 57 t/h. Of the
crushed product, 63.4% by weight had a size that was smaller than
4 mm, accordingly the production of material having a size smaller
than 4 mm being 57 t/h.times.63.4% by weight=36.1 t/h. The crushed
material in test 2 had an LT index of 85% by weight in the fraction
5-8 mm. FIG. 9 shows the pressure variation in the hydraulic fluid
as a function of time. The average pressure was approx. 4.87 MPa
and the standard deviation of the same average pressure was 0.92
MPa.
[0070] As is seen in the above, approximately equally much, approx.
36 t/h, crushed material was produced having a size that was smaller
than 4 mm in test 1 and test 2. However, in test 1 the crusher consumed
only 135 kW versus approx. 150 kW in test 2. In test 1 only 48
t/h was fed into the crusher while 57 t/h was fed into the crusher
in test 2. This means that also auxiliary equipment, such as conveyors
etc., consumed more energy in test 2. The reason for the higher
flow of material in test 2 was that a great share of the material
that was fed to the crusher was not crushed to the desired size
but had to be recirculated for an additional crushing. The greater
flow of material in test 2 which accordingly was due to the inferior
crushing and the greater recirculation following thereby, entails
an increased wear on the crusher and the shells according to prior
art in comparison with the invention. As is also seen in FIG. 7
the crusher in test 1 could crush the material to smaller sizes
than in test 2. The produced material had also a considerably better
grain shape (i.e., LT index) in test 1 than in test 2. The considerably
lower variation in hydraulic fluid pressure in test 1 (standard
deviation 0.61 MPa, see also FIG. 8) than in test 2 (standard deviation
0.92 MPa, see also FIG. 9) means a considerably lower mechanical
load on the crusher generally and the hydraulic setting device in
particular.
[0071] Although the present invention has been described in connection
with preferred embodiments thereof, it will be appreciated by those
skilled in the art that additions, modifications, substitutions,
and deletions may be made without departing from the spirit and
scope of the invention as defined in the appended claims. |