Abstrict A method of crushing material includes the steps of feeding a first
flow of material to be crushed to a rotor rotating around a vertical
axis, the rotor accelerating the first flow of material towards
an impact wall section, and feeding a second flow of material to
be crushed into the path of the accelerated first flow of material.
The second flow of material is fed in a direction having a substantially
tangential component in relation to the rotor, such that the second
flow of material will have a substantially tangential component
of movement in relation to the rotor when reaching the path of the
first flow of material. A crusher is adapted to feed the second
flow of material such that it will have a substantially tangential
component of movement in relation to the rotor when reaching the
path of the first flow of material.
Claims 1. A vertical shaft impact crusher for crushing material, said
crusher comprising: a rotor for accelerating a first flow of material
to be crushed, a first feed means for vertically feeding the first
flow of material to the rotor, a housing comprising a wall with
a circumferential impact wall section against which the accelerated
first flow of material may be crushed, a second feed means for feeding
a second flow of material to be crushed into the path of the accelerated
first flow of material, wherein the second feed means comprises
means for forming at least one hillside on which the second flow
of material may slide, the hillside having a slope being substantially
tangential in relation to the rotor for directing the second flow
of material in a direction having a substantially tangential component
in relation to the rotor, such that the second flow of material
will have a substantially tangential component of movement in relation
to the rotor when reaching the path of the first flow of material.
2. A crusher according to claim 1 wherein the wall of the housing
comprises a circumferential distributing wall section forming part
of the second feed means and being located above said impact wall
section, the second feed means comprising feed hopper means for
feeding, in a first step, the second flow of material in a direction
towards the distributing wall section, which is adapted to receive
the second flow of material and to direct it against the impact
wall section.
3. A crusher according to claim 2 wherein the feed hopper means
comprises an inner hopper and an outer hopper surrounding the inner
hopper, said hoppers having a common vertical axis substantially
coinciding with the vertical axis of the rotor, the inner hopper
being provided with at least one outlet for allowing the second
flow of material fed to the inner hopper to enter a space formed
between the inner and the outer hoppers, an "L"-shaped
direction arm being fixed in the space between said hoppers just
outside said outlet to facilitate the building of a hillside of
accumulated material, the hillside having a slope being tangential
in relation to the rotor for directing the second flow of material
towards the distributing wall section.
4. A crusher according to claim 3 wherein a horizontal leg of
the "L"-shaped direction arm is pointing in the rotational
direction of the rotor, such that any dust entrained by the rotor
in a direction having an upwardly directed component and a component
being tangential in relation to the rotor will be hindered by a
vertical leg of the direction arm.
5. A crusher according to claim 3 wherein the inner and outer
hoppers have a polygonal shape as seen from above.
6. A crusher according to claim 2 wherein the second feed means
further comprises the upper surface of a ring fixed to the inner
side of the wall of said housing to separate the distributing wall
section from the impact wall section located below it.
7. A crusher according to claim 6 wherein the second feed means
further comprises at least one vertical collection plate extending
radially with respect to the rotor, the collection plate being fixed
to the upper face of the ring at such a location that a part of
the second flow of material fed towards the distributing wall section
in said first step will accumulate against the collection plate
to form a hillside of material, the hillside having a slope being
substantially tangential in relation to the rotor for giving the
second flow of material a substantially tangential component of
movement in relation to the rotor when reaching the path of the
first flow of material.
8. A method of crushing material, said method comprising the steps
of feeding a first flow of material to be crushed to a rotor rotating
around a vertical axis, in said rotors accelerating said first flow
of material towards an impact wall section of a housing surrounding
the rotor, feeding a second flow of material to be crushed into
the path of the accelerated first flow of material wherein feeding
the second flow of material in a direction having a substantially
tangential component in relation to the rotor, such that the second
flow of material will have a substantially tangential component
of movement in relation to the rotor when reaching the path of the
first flow of material.
9. A method according to claim 8 wherein the second flow of material
is fed into the path of the first flow of material adjacent to the
impact wall section.
10. A method according to claim 8 wherein the second flow of material
is fed from a position adjacent to the axis of the rotor towards
a wall of the housing in a direction having a substantial tangential
component in relation to the rotor.
Description TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vertical shaft impact crusher
for crushing material, said crusher comprising
[0001] a rotor for accelerating a first flow of material to be
crushed, [0002] a first feed means for vertically feeding the first
flow of material to the rotor, [0003] a housing comprising a wall
with a circumferential impact wall section against which the accelerated
first flow of material may be crushed, [0004] a second feed means
for feeding a second flow of material to be crushed into the path
of the accelerated first flow of material.
[0005] The present invention further relates to a method of crushing
material, said method comprising the steps of [0006] feeding a first
flow of material to be crushed to a rotor rotating around a vertical
axis, [0007] in said rotor accelerating said first flow of material
towards an impact wall section of a housing surrounding the rotor,
[0008] feeding a second flow of material to be crushed into the
path of the accelerated first flow of material.
BACKGROUND ART
[0009] Vertical shaft impact crushers (VSI-crushers) are used in
many applications for crushing hard material like rocks, ore etc.
U.S. Pat. No. 3154259 describes a VSI-crusher comprising a housing
and a horizontal rotor located inside the housing. Material that
is to be crushed is fed into the rotor via an opening in the top
thereof. With the aid of centrifugal force the rotating rotor ejects
the material against the wall of the housing. On impact with the
wall the material is crushed to a desired size. The housing wall
could be provided with anvils or have a bed of retained material
against which the accelerated material is crushed.
[0010] To increase the amount of material crushed by the crusher
two separate material flows could be fed to the crusher. A first
material flow is fed to the rotor. The first material flow is accelerated
by the rotor and is ejected towards the housing wall. A second material
flow is fed outside the rotor, i.e. between the rotor and the housing.
This second material flow is hit by the first material flow ejected
by the rotor. Thus the first and second material flows are crushed
against each other just outside the rotor.
[0011] U.S. Pat. No. 2012694 to Runyan describes a crusher where
a first flow of material is fed to the centre of a rotating rotor.
A second flow of material is fed at the wall of a crusher housing
via a feeder comprising two spaced cones. At the housing wall the
second flow of material is hit by the first flow of material ejected
by the rotor.
[0012] U.S. Pat. No. 3429511 to Budzich describes a crusher where
a first flow of material is fed to the centre of a rotating rotor.
A second flow of material is fed via a feeding gap extending around
the rotor. The second flow of material forms a continuous curtain
of flowing material covering the pathway of the first flow of material
just outside the rotor. The first flow of material ejected by the
rotor thus hits and crushes the second flow of material.
[0013] U.S. Pat. No. 4662571 to MacDonald describes a crusher
were a first flow of material is fed to the centre of a rotating
rotor. A second flow of material is fed into the path of the first
material flow accelerated by said rotor before said first material
impacts against the crusher wall.
[0014] The above crushers do not to utilize the energy of the first
flow of material in a very efficient way.
SUMMARY OF THE INVENTION
[0015] It is an object of the present invention to provide a crusher
which utilizes the energy of a first flow of material accelerated
by a rotor in a more efficient way.
[0016] This object is achieved by a crusher according to the preamble
and characterized in that [0017] the second feed means comprises
means for forming at least one hillside on which the second flow
of material may slide, the hillside having a slope being substantially
tangential in relation to the rotor for directing the second flow
of material in a direction having a substantially tangential component
in relation to the rotor, such that the second flow of material
will have a substantially tangential component of movement in relation
to the rotor when reaching the path of the first flow of material.
[0018] The present invention thus provides a second flow of material
having a substantially tangential component of movement. This improves
the crushing action and makes it possible to direct the second flow
of material towards positions suitable for impact and away from
the periphery of the rotor and the internal structures, such as
internal beams of the crusher. The versatility of the crusher is
improved resulting in the ability to increase the throughput and
to alter the size distribution curve of the crushed product.
[0019] Preferably the wall of the housing comprises a circumferential
distributing wall section forming part of the second feed means
and being located above said impact wall section, the second feed
means comprising means for feeding, in a first step, the second
flow of material in a direction towards the distributing wall section,
which is adapted to receive the second flow of material and to direct
it against the impact wall section.
[0020] The distributing wall section makes it possible to give
the second flow of material a desired velocity and the desired direction
just before it is to enter the impact wall section.
[0021] Preferably the feed hopper means comprises an inner hopper
and an outer hopper surrounding the inner hopper, said hoppers having
a common vertical axis substantially coinciding with the vertical
axis of the rotor, the inner hopper being provided with at least
one outlet for allowing the second flow of material fed to the inner
hopper to enter a space formed between the inner and the outer hopper,
an "L"-shaped direction arm being fixed in the space between
said hoppers just outside said outlet to facilitate the building
of a hillside of accumulated material, the hillside having a slope
being tangential in relation to the rotor for directing the second
flow of material towards the distributing wall section.
[0022] The inner and outer hopper provides an efficient way of
distributing the desired amount of material for forming the second
flow of material. The hillside formed on the direction arm provides
an efficient base for giving the second flow of material the desired
direction without causing wear to internal components including
the direction arm itself.
[0023] Preferably a horizontal leg of the "L"-shaped
direction arm is pointing in the rotational direction of the rotor,
such that any dust entrained by the rotor in a direction having
an upwardly directed component and a component being tangential
in relation to the rotor will be hindered by a vertical leg of the
direction arm.
[0024] The vertical leg of the direction arm will efficiently decrease
the dust emission from the inner hopper. Thus expensive filtering
means for filtering emitted air may be omitted. It also becomes
much easier to inspect the crusher during operation and to observe
the amount of material forming the second flow of material.
[0025] Preferably the inner and outer hoppers have a polygonal
shape as seen from above. The polygonal shape is preferable since
it makes the manufacturing of outlets formed in the inner hopper
and in particular hatches for covering said outlets much easier
since they all can be made flat. The polygonal shape also assists
in reducing dust emissions from the crusher since the internal corners
of the polygonal hoppers will get filled with dust thereby creating
dead pockets of retained dust, which help absorbing the air flow
created by the rotor. The polygonal shape also helps deflecting
the air streams swirling around inside the crusher. The dead pockets
of retained dust will also protect the inner and outer hopper from
wear.
[0026] Preferably the second feed means further comprises the upper
surface of a ring fixed to the inner wall of said housing to separate
the distributing wall section from the impact wall section located
below it. The ring provides a base for the distributing wall section
and prevents any material from the impact wall section from bouncing
up to the distributing wall section. Also material from the distributing
wall section will be prevented from entering the impact wall section
in places where it is not desired. The separation of the distributing
wall section from the impact wall section thus makes the crushing
more efficient and decreases wear on internal parts of the crusher.
[0027] Preferably the second feed means further comprises at least
one vertical collection plate extending radially with respect to
the rotor, the collection plate being fixed to the upper face of
the ring at such a location that a part of the second flow of material
fed towards the distributing wall section in said first step will
accumulate against the collection plate to form a hillside of material,
the hillside having a slope being substantially tangential in relation
to the rotor for giving, in a second step, the remaining part of
the second flow of material a substantially tangential component
of movement in relation to the rotor when reaching the path of the
first flow of material. The hillside formed will protect the internal
parts, including the collection plate and the upper surface of the
ring from wear. The hillside will also provide the desired direction
for the second flow of material before the second flow of material
enters the impact wall section.
[0028] A further object of the present invention is to provide
a method of crushing material which improve the utilization of the
energy supplied during the crushing.
[0029] This object is achieved with a method according to the preamble
and characterized in feeding the second flow of material in a direction
having a substantially tangential component in relation to the rotor,
such that the second flow of material will have a substantially
tangential component of movement in relation to the rotor when reaching
the path of the first flow of material. The inventive method makes
it possible to direct the second flow of material towards positions
attractive for impact and away from internal structures such as
internal beams of the crusher. Thus crushing action and utilization
of crushing energy is improved and wear inside the crusher is reduced.
[0030] Preferably the second flow of material is fed into the path
of the first flow of material adjacent to the impact wall section.
An advantage with this is that the second flow of material will,
after being hit by the first flow of material, impact against the
impact wall section. Thus the second flow of material will be crushed
against the impact wall section and it will also be subjected to
further hits of the first flow of material. The retention time of
the second flow of material at the impact wall section will thus
be increased. This is a large advantage over prior art crushers
where a second flow of material randomly falls freely between the
rotor and the crusher wall. This random falling of the prior art
crushers results in that a major part of a second flow of material
will never be hit by the first flow of material. The randomly falling
second flow of material of the prior art crushers will also deflect
the first flow of material thus reducing or eliminating the crushing
against the crusher wall. Another advantage of the present invention
is that the risk that the second flow of material accidentally impacts
the rotor is decreased. Also the risk of the first flow of material
accidentally rebounding against the rotor or other internal structures
after hitting the second flow of material is decreased. Thus the
wear on the crusher and in particular on the rotor is decreased.
[0031] Preferably the second flow of material is fed from a position
adjacent to the axis of the rotor towards a wall of the housing
in a direction having a substantial tangential component in relation
to the rotor. The central feeding of the material makes it possible
to feed in one position and then divide the flow of material into
a first flow of material and a second flow of material. The feeding
towards the wall increases the chance of placing the second flow
of material in a position suitable for best crushing performance.
In particular the chance of the second flow of material reaching
the path of the first flow of material adjacent to the impact wall
is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The invention will hereafter be described in more detail
and with reference to the appended drawings.
[0033] FIG. 1 is three-dimensional section view and shows a rotor
for a VSI-crusher FIG. 2 is a three-dimensional view and shows the
rotor of FIG. 1 with the upper disc removed.
[0034] FIG. 3 shows the view of FIG. 2 as seen from above in a
two dimensional perspective.
[0035] FIG. 4 is a three dimensional view, partly in section, and
shows a vertical shaft impact crusher.
[0036] FIG. 5 is a section view and shows the crusher of FIG. 4.
[0037] FIG. 6 is a schematic section view and shows the build up
of a bed of retained material against an impact wall section.
[0038] FIG. 7 is a section view taken along the line VII-VII of
FIG. 5.
[0039] FIG. 8 is a three dimensional view, partly in section, and
shows the pathway of the second flow of material of the vertical
shaft impact crusher.
[0040] FIG. 9 is a top view, partly in section, and shows the pathway
of the second flow of material of the vertical shaft impact crusher.
[0041] FIG. 10 is a side view showing a direction arm in detail.
[0042] FIG. 11 is a top view, partly in section, and shows the
pathways of the first and the second flows of material according
to an alternative embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0043] FIG. 1 shows a rotor 1 for use in a VSI-crusher. The rotor
1 has a roof in the form of an upper disc 2 having a top wear plate
3 and a floor in the form of a-lower disc 4. The lower disc 4 has
a hub 6 which is welded to the disc 4. The hub 6 is to be connected
to a shaft (not shown) for rotating the rotor 1 inside the housing
of a VSI-crusher.
[0044] The upper disc 2 has a central opening 8 through which material
to be crushed can be fed into the rotor 1. The upper disc 2 is protected
from wear by upper wear plates 10 and 12. The upper disc 2 is protected
from rocks impacting the rotor 1 from above by the top wear plate
3. As is better shown in FIG. 2 the lower disc 4 is protected from
wear by three lower wear plates 14 16 and 18.
[0045] The upper and lower discs 2 4 are separated by and held
together by a vertical rotor wall which is separated into three
wall segments 20 22 and 24. The gaps between the wall segments
20 22 24 define outflow openings 26 28 30 through which material
may be ejected against a housing wall.
[0046] At each outflow opening 26 28 30 the respective wall segment
20 22 24 is protected from wear by three wear tips 32 34 36
located at the trailing edge of the respective wall segment 20
22 24.
[0047] A distributor plate 38 is fastened to the centre of the
lower disc 4. The distributor plate 38 distributes the material
that is fed via the opening 8 in the upper disc 2 and protects the
lower disc 4 from wear and impact damages caused by the material
fed via the opening 8.
[0048] During operation of the rotor 1 a bed 40 of material is
built up inside the rotor 1 against each of the three wall segments
20 22 24. In FIG. 3 only the bed 40 located adjacent to the wall
segment 20 is shown. The bed 40 which consists of material that
has been fed to the rotor 1 and then has been trapped inside it,
extends from a rear support plate 42 to the wear tips 32 34 36.
The bed 40 protects the wall segment 20 and the wear tips 32 34
36 from wear and provides a proper direction to the ejected material.
The dashed arrow A describes a typical passage of a piece of rock
fed to the rotor 1 via the central opening 8 and ejected via the
outflow opening 26. The arrow R indicates the rotational direction
of the rotor 1 during operation of the VSI-crusher.
[0049] Each wall segment 20 22 24 is provided with a cavity wear
plate 44 46 48 each consisting of three cavity wear plate portions.
The cavity wear plates 44 46 48 protects the rotor 1 and in particular
the wear tips 32 34 36 from material rebounding from the housing
wall and from ejected material and airborne fine dust spinning around
the rotor 1.
[0050] In FIG. 4 a vertical shaft impact crusher 50 is shown. The
rotor 1 is located inside a housing 52 of the crusher 50. At the
top of the crusher 50 a feed hopper means 54 is located. The feed
hopper means 54 has a hexagonal inner hopper 56 and a hexagonal
outer hopper 58. A roof, not shown in FIG. 4 seals a space 60 formed
between the inner hopper 56 and the outer hopper 58 from above.
The inner hopper 56 is provided with six outlets 62 each outlet
62 being located at a side of the hexagonal inner hopper 56. Each
outlet 62 is provided with a movable hatch 64. The movable hatch
64 may be placed in three different positions on the inner hopper
56 to obtain a desired open area of the respective outlet 62. An
"L"-shaped direction arm 66 is fixed between the inner
hopper 56 and the outer hopper 58 adjacent to each outlet 62. Below
the inner hopper 56 a central feeding cylinder 68 is placed. The
feeding cylinder 68 is fixed to the inside of the wall 70 of the
housing 52 with the aid of three beams of which only the beam 72
is shown in FIG. 4.
[0051] A circumferential distributing wall section 74 is located
at the same level as the feeding cylinder 68. Below the distributing
wall section 74 and on the same level as the rotor 1 a circumferential
impact wall section 76 is located. A cavity ring 78 separates the
distributing wall section 74 from the impact wall section 76. A
number of vertical collection plates 80 which extend radially with
respect to the rotor 1 are fixed to the upper surface 82 of the
ring 78.
[0052] A bed retention ring 84 is located at the bottom of the
crusher 50. A number of bed support plates 86 are located between
the bed retention ring 84 and the cavity ring 78. A throttle means
88 partly shown in FIG. 4 is located between the inner hopper
56 and the feeding cylinder 68.
[0053] FIG. 5 shows that the throttle means 88 controls a sliding
throttle 90 located at the bottom 92 of the inner hopper 56. Material
to be crushed is fed to the inner hopper 56 in the direction of
the arrow M. The roof 94 prevents material from falling directly
into the space 60 between the inner hopper 56 and the outer hopper
58. The roof 94 also prevents dust from flowing out of the top of
the crusher 50. The opening position of the sliding throttle 90
determines the amount of material forming a first flow of material
M1 that will reach the rotor 1 via an inlet 96 at the bottom 92
of the inner hopper 56 and the feeding cylinder 68 in relation to
the amount of material forming a second flow of material M2 that
will reach the space 60 via the outlets 62.
[0054] FIG. 6 shows how the rotor 1 being rotated with the aid
of a not shown shaft connected to the hub 6 will accelerate the
first flow of material M1 against the impact wall section 76. Quite
soon after the crusher operation has been started some crushed material
will accumulate against the impact wall section 76 to form a wall
bed 98 of retained material as shown in FIG. 6. The bed support
plates 86 the bed retention ring 84 and the cavity ring 78 will
support the bed and provide a desired shape. The first flow of material
M1 will be accelerated by the rotor 1 and impact against the wall
bed 98 of retained material. Thus a so called autogenous crushing
is obtained wherein the first flow of material M1 is crushed against
a wall bed 98 formed from part of the material previously crushed.
[0055] FIG. 7 shows, as seen from above, the sliding throttle 90
and the inlet 96 at the bottom 92 of the inner hopper 56. An inspection
hatch 100 makes it possible to inspect the rotor 1 and perform maintenance
inside the crusher 50. In FIG. 7 the roof 94 has been partially
removed to visualize an advantageous effect of the polygonal hoppers
56 58. Between two adjacent direction arms 66 a dead pocket 101
of accumulated material has been built up during crusher operation.
The dead pocket 101 being formed between the polygonal hoppers
56 and 58 protects the direction arm 66 the roof 94 and the hoppers
56 58 against wear caused by the second flow of material M2.
[0056] The operation of the crusher 50 will now be described in
more detail with reference to FIG. 8 to 10. As described with reference
to FIG. 5 the feed of material M is divided in a first flow of material
M1 and a second flow of material M2. The second flow of material
M2 passes out of the outlets 62 and lands on the direction arms
66. Each direction arm 66 has, as is best shown in FIG. 10 a vertical
leg 102 and a horizontal leg 104. At an end of the horizontal leg
104 a projection 106 has been welded. The second flow of material
M2 will initially build a hillside 108 of material on the direction
arm 66. Once the hillside 108 is in place, after few minutes of
crusher operation, the second flow of material M2 will slide on
the hillside 108 thus obtaining a movement having a substantially
tangential component in relation to the rotor 1 as can be seen
from FIG. 8 and FIG. 9. The second flow of material M2 will thus
in this first step be directed towards the distributing wall section
74. At the location of the distributing wall section 74 where the
second material flow would impinge the wall section 74 the collection
plate 80 is located. During the first minutes of crusher operation
the second flow of material M2 will build a second hillside 110
of material against the collection plate 80 and the upper surface
82 of the cavity ring 78 as is best shown in FIG. 8. After the second
hillside 110 has been established the rest of the second flow of
material M2 will, in a second step, slide on the second hillside
110. The second material flow M2 will thus, in this second step,
obtain a movement having a substantially tangential component in
relation to the rotor 1. The second material flow M2 will then pass
on down into a position adjacent to the impact wall section 76.
Adjacent to the impact wall section 76 the second flow of material
M2 having a movement with a substantially tangential component will
be hit by the first flow of material M1 ejected by the rotor. When
the second flow of material M2 is hit by the first flow of material
M1 it will be forced against the wall bed 98. Since the second flow
of material M2 is fed adjacent to the impact wall section 76 the
second flow of material M2 will land on the wall bed 98 either directly
or after being hit by the first flow of material M1 and be exposed
to the impact of the first flow of material M1 for a long period
of time thus achieving an efficient crushing. It will be appreciated
that, as clearly demonstrated in FIG. 6 any part of the second
flow of material M2 that by accident is not immediately hit by the
first flow of material M1 will also land on the wall bed 98 thus
getting more chances of being hit by the first flow of material
M1. This effect is enhanced by the fact that the second flow of
material M2 is given a tangential component of movement by the second
hillside 110 and is thus directed against the wall bed 98. Thus
any part of the second flow of material M2 that is not hit by the
first flow of material M1 (as illustrated in FIG. 9) will instead
directly impact the wall bed 98 and be retained there for some time.
The increased retention time of the second material flow M2 on the
wall bed 98 is particularly important since the first flow of material
M1 will appear to be pulsed when leaving the rotor 1. Since the
rotor 1 is rotated and the first flow of material M1 is ejected
through the three outflow openings 26 28 30 of the rotor 1 a
given portion of the wall bed 98 will become hit by the first flow
of material M1 three times per each revolution of the rotor 1 i.e.
if the rotor rpm is 1500 a given portion of the wall bed 98 will
become hit 3.times.1500=4500 times per minute. The increased retention
time of the second flow of material M2 on the wall bed 98 ensures
that the second flow of material M2 will become hit by the first
flow of material M1 before leaving the crusher. In fact the second
flow of material M2 will be hit many times by the first flow of
material M1 thus ensuring an efficient crushing. FIG. 8 further
shows that the internal beam 72 has such a location in relation
to the collection plate 80 that the beam 72 is not hit by the second
flow of material M2.
[0057] As is indicated with a dashed arrow in FIG. 9 the movement
of the first flow of material M1 will have a substantially tangential
component. Since the second flow of material M2 has a movement with
a substantially tangential component having the opposite direction,
the first flow of material M1 will impact the second flow of material
M2 in a head-on collision thus further improving the crushing action.
The fact that the first and second flows of material M1 M2 travel
in opposite directions before impacting each other provides an optimum
initial impact energy.
[0058] From FIG. 10 another important aspect of the direction arm
66 is shown. The rotation of the rotor 1 will cause entrainment
of dust particles. The particles will swirl along the rotational
direction, shown with a dashed arrow R in FIG. 10 of the rotor
1 and move up an down in the crusher 50. The vertical leg 102 of
the direction arm 66 and the horizontal leg 104 pointing in the
direction of the rotational direction R will however deflect the
dust particles and force them down into the crusher 50 as indicated
with an arrow D in FIG. 10. Thus the dust emissions from the crusher
50 will be substantially reduced thanks to the direction arm 66.
The dead pocket 101 built up against the vertical leg 102 improves
the deflection of the dust particles and also protects the vertical
leg 102 the roof 94 the inner hopper 56 and the outer hopper 58
(not shown in FIG. 10) from wear. The polygonal shapes of the inner
hopper 56 and the outer hopper 58 will tend to diffuse the air rotating
inside the crusher. The polygonal shape thus assists in decreasing
the dust emission from the crusher.
[0059] It will be appreciated from FIG. 9 that a minor part of
the second flow of material M2 sliding on the hillside 108 may not
reach the distributing wall section 74 and the second hill 110.
This minor part of the second flow of material M2 will, however,
also have a movement with a substantially tangential component and
will be directed directly towards the impact wall section 76 where
it is hit by the first flow of material M1.
[0060] FIG. 11 illustrates an alternative embodiment of the invention.
A vertical shaft impact crusher 150 similar to the crusher 50 shown
in FIG. 4-10 is equipped with a rotor 111. The rotor 111 is similar
to the rotor 1 that is illustrated in FIG. 1-3 but is adapted to
be rotated in the opposite direction R', i.e. clockwise. The rotor
111 will thus produce a first flow of material M1' that has another
direction than the first flow of material M1 shown in FIG. 9. As
is indicated with a dashed arrow in FIG. 11 the movement of the
first flow of material M1' will have a substantially tangential
component. Since the second flow of material M2 has a movement with
a substantially tangential component having the same direction,
the first flow of material M1' will impact the second flow of material
M2 in a "from behind" collision. The fact that the first
and second flows of material M1', M2 travel in the same direction
before impacting each other provides a reduced impact action compared
to the head-on collision illustrated in FIG. 8-9 but instead an
improved grinding and attrition action. The grinding and attrition
action provides an improved shape, i.e. an improved roundness, to
the material that is fed to the crusher. Thus the embodiment illustrated
in FIG. 11 is particularly suitable for cases where the material
to be crushed requires a moderate to low reduction in size but an
increased roundness. It will be appreciated that an alternative
way of achieving the "from behind" collision is to keep
the rotor 1 having the direction of rotation R in the crusher and
instead alter the direction of the direction arm 66 and change the
position of the collection plate 80 to obtain a second flow of material
having the opposite direction compared to the second flow of material
M2 shown in FIGS. 9 and 11.
[0061] It will be appreciated that numerous modifications of the
embodiments described above are possible within the scope of the
appended claims.
[0062] In an alternative embodiment of the invention only the hillside
108 is used. In such an embodiment the hillside 108 formed on the
direction arm 66 directs the second flow of material M2 directly
towards the impact wall section 76 without going via the distributing
wall section, which may be omitted in this alternative embodiment.
The second flow of material M2 thus having a movement with a substantially
tangential component will reach the path of the first flow of material
M1 adjacent to the impact wall section 76 and be subjected to multiple
hits by the first flow of material M1 at the wall bed 98 just like
in the embodiment described above.
[0063] In still another embodiment of the invention only the hillside
110 is used. In such an embodiment the second flow of material M2
is dropped vertically on the upper surface 82 of the cavity ring
78. A collection plate 80 located on the surface 82 will provide
a basis for the accumulation of a hillside 110. The second flow
of material M2 falling vertically on the hillside 110 will slide
on the hillside 110 thus obtaining a movement having a substantially
tangential component in relation to the rotor 1. The second flow
of material M2 will then enter the impact wall section 76 and be
crushed in accordance with what has been described above.
[0064] The inner and outer hopper may in alternative embodiments
have other polygonal shapes such as square, pentagonal etc. The
inner and outer hoppers may also be circular. The polygonal shape
is preferable since it makes the manufacturing of the outlets and
in particular the hatches much easier since they can be made flat.
The polygonal shape also reduces the wear on the hopper and the
dust emission from the crusher.
[0065] In an alternative embodiment the horizontal leg 104 of the
direction arm 66 may have a length which is adjustable. Thus the
length of the horizontal leg could be adjusted to accommodate different
feed material types and sizes. The length of the horizontal leg
could also be adjusted to optimise the reduction of dust emission
from the crusher.
[0066] Above it has been described that the hillsides 108 110
on which the second flow of material M2 slides are formed by material
accumulating on the direction arm 66 and against the cavity ring
78 and the collection plate 80 respectively. It is however also
possible to form a prefabricated hillside of e.g. a steel sheet,
a ceramic tile or a similar plate, said hillside having a desired
tangential slope in relation to the rotor immediately from the start
of the crusher. However, hillsides 108 and 110 that are made up
of accumulated material have the advantage of avoiding the wear
problems that would be associated with prefabricated hillsides made
of a steel sheet or an other material. |