Abstrict A rock crusher (10) including a turntable (26) with a series of
impellers (34) mounted thereon. Each impeller (34) includes a curved,
C-shaped pocket (56) that includes a radially inwardly sloped wall
(59) terminating in a transversely extending lip (111). The impeller
(34) is oriented in a somewhat closed position or greater angle
of attack (90) so that the front face (54) of the impeller is exposed
to oncoming rocks. A method of retaining rock fines (116) in a pocketed
impeller (34) of a rock crusher (10) which includes orienting a
radially outermost pocket wall (59) in a radially inwardly sloped
orientation is disclosed.
Claims What is claimed is:
1. A rock hurling impact rock crusher comprising,
a rotatable turntable including a center region adapted to receive
a quantity of rocks and an outer region,
a plurality of impellers mounted to the turntable at the outer
region thereof for rotation of the impellers as the turntable is
rotated, each of the impellers having a forwardly facing wear face
substantially radially oriented relative to the turntable,
a ring of anvils spaced outwardly of the impellers and substantially
in vertical alignment therewith,
each impeller having a body with a pocket formed in the wear face
thereof, the pocket increasing in depth from a radially inner shallow
end to a radially outer deepest end, and the pocket being defined
at the radially outer end by a transversely extending lip and an
end wall extending inwardly in the body from the lip in a radially
outwardly extending direction, whereby fines carried with rocks
being crushed collect within and are at least partially trapped
by the pockets of the impellers.
2. The rock crusher of claim 1 wherein,
the pocket gradually tapers in depth from the shallow end to the
deepest end; and
the end wall in the pocket is concaved with a portion thereof being
radially outward of the lip.
3. The rock crusher of claim 1 wherein,
the impeller is substantially wedge-shaped and the wear face on
each impeller is oriented at an angle of attack exposing the wear
surface and the pocket to oncoming rocks.
4. The rock crusher as defined in claim 3 wherein,
the combination of the angle of attack and the shape of the pocket
result in the end wall of the pocket extending inwardly from the
lip in a radially outward direction.
5. The rock crusher of claim 1 wherein,
the wear face of each impeller has an angle of attack of about
8 degrees.
6. The rock crusher as defined in claim 1 wherein,
the wear face of the impeller included a convex surface radially
outwardly of the pocket.
7. An impeller for use in a centrifugal impact rock crusher comprising:
an impeller body formed for mounting to a turntable of a centrifugal
impact rock crusher with a front wear face substantially radially
oriented so as engage and hurl rocks outwardly against an anvil
when mounted on the turntable, and the body being further formed
with a pocket providing a recess in the front wear face, the pocket
tapering in depth from a shallow end to a deepest end, and the pocket
being defined in part by a transversely extending end wall at the
deepest end of the pocket, the body further being formed for mounting
of the impeller to the turntable with the deepest end of the pocket
in a radially outermost position and the end wall being radially
outwardly inclined as said end wall extends inwardly into the body.
8. The impeller of claim 7 wherein,
the end wall of the pocket is concaved.
9. The impeller of claim 7 wherein,
the body of the impeller is formed for mounting of the impeller
to the turntable with the wear face oriented at an angle of attack
to a radial line from a center of the turntable of about 8 degrees.
10. The impeller of claim 7 wherein,
the wear face includes a convex surface radially outwardly of the
pocket.
Description TECHNICAL FIELD
This invention pertains to centrifugal impact rock crushers and,
more particularly, to an improved pocketed impeller blade or ejector
for the turntables of such crushers and a method for retaining rock
fines in the impeller pockets.
BACKGROUND ART
A centrifugal impact rock crusher is a device that accepts large
size rocks, for example rocks approximately 2-5 inches in diameter,
and breaks them apart into small, pieces, such as pieces approximately
1 inch or less in diameter. In operation, large rocks are fed downwardly
through a hopper and feed tube and onto a feed cone at the center
of an impeller turntable. A series of spaced impeller blades or
members are positioned along the periphery of the turntable just
off the feed cone. After landing on the feed cone, the rocks are
deflected radially outwardly off of the feed cone and into the path
of the rotating impellers. The impellers catch the rocks and throw
them with tremendous centrifugal force radially outwardly and violently
against fixed anvils. The turntable is positioned inside a large
cylindrical housing that has a ring of anvils fixedly mounted along
the inside of the housing wall in vertical alignment with the impellers.
When the rocks strike the anvils, they crack under their own momentum
into relatively uniform, often cubical, pieces and freely fall down
onto a conveyor or other suitable output device, such as a receptacle.
The impeller blades of prior art rock crushers are generally wedge-shaped
rectangular blocks that are mounted to the turntable with their
narrow wedge ends adjacent or even partially overlapping the feed
cone and their wide ends at the outer edge of the turntable. The
purpose of the impellers is not to break apart the rocks, but to
catch or grab the rocks and throw them outwardly against the anvils,
which are fixedly mounted along the circumferential wall surrounding
the turntable. While the anvils are designed to withstand tremendous
impact forces, the impellers are mainly designed to withstand abrasion
forces associated with slinging of the rocks outwardly against the
anvils. Abrasion is caused not only by the rocks themselves, but
also by the "fines" associated with the rocks. Fines includes
dust and sand particles, dirt and mud, smaller rock fragments all
of which may be carried by the large rock pieces into the rock crushing
device.
It has been proposed to reduce wear on the impellers by creating
a pocket within the impact or wear surface of the impeller. With
pocketed impellers, fines collect in the pocket and thereby create
a renewable wear surface of fines that contacts the rocks. As the
rocks are slung by the impellers, the rocks sweep away a portion
of the fines from the pocket. However, additional fines carried
by the rocks subsequently refill the pocket. Canica-Jaques of Vancouver,
Wash., U.S.A., for example, makes a rock crusher impeller with two
radially adjacent pockets in the impeller wear surface. This type
of rock crusher impeller, however, is limited in the size and type
of rock that it can crush--rocks no larger than about 21/2 inches
in diameter and relatively soft rock, such as limestone, cement,
sulfur, etc. are best suited for crushing using the Canica-Jaques
pocketed impellers. The Canica-Jaques'impellers also require rock
material with a high fines content in order to replace the fines
swept out of the pockets by the rocks, and with high moisture content
in order to help hold the fines in the pockets.
However, prior art pocketed impellers have not been found to work
satisfactorily with certain types of rock, namely, large, relatively
hard and dry rock material. The present invention is designed to
address these limitations of prior art centrifugal impact rock crusher
impellers.
DISCLOSURE OF INVENTION
A rock crusher and an improved pocketed impeller for a rock crusher
are provided which include, briefly, a rotatable turntable, a series
of impellers mounted for rotation on the turntable, a ring of stationary
anvils positioned around and radially outwardly of the impellers.
The improved impeller is formed with a pocket in a forwardly facing
wear surface which engages and propels the rocks. The pocket is
formed to have an enhanced ability to trap and retain rock fines
in the pocket. More particularly, the pocket includes a radially
outermost wall that is inwardly sloped or tilted when the impeller
is attached to the rock crusher turntable. This inward tilt or negative
slope traps rock fines against being swept from the pocket under
centrifugal forces. Moreover, the incoming rocks tend to pack the
fines trapped in the pocket.
The invention also includes the method of trapping fines in a pocketed
impeller which is comprised of the step of securing the impeller
to the rock crusher turntable with a radially outermost wall of
a fines-trapping pocket oriented to be radially inwardly sloped.
These and other features, objects, and advantages of the present
invention will become apparent from the following description of
the best mode for carrying out the invention, when read in conjunction
with the accompanying drawings, and the claims, which are all incorporated
herein as part of the disclosure of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Throughout the several views, like reference numerals refer to
like parts, wherein:
FIG. 1 is a schematic side elevation view, in half section, of
a centrifugal impact rock crusher employing the improved impellers
of the present invention;
FIG. 2 is a cut-away pictorial view of the rock crusher of FIG.
1;
FIG. 3 is pictorial view of the impeller of the present invention;
FIG. 4 is a top plan view of the turntable on which five impellers
like the impeller of FIG. 3 are mounted;
FIG. 5 is a top plan view of the impeller of FIG. 3 shown mounted
to a mounting bracket, which secures the impeller to the turntable;
FIG. 6 is an exploded, fragmentary view of the mounting arrangement
for securing the impeller of FIG. 5 to its mounting bracket;
FIG. 7 is a schematic view of the impeller of FIG. 3 showing its
angle of attack relative to a radial line of the turntable;
FIG. 8 is a schematic view of a prior art impeller, showing the
design of its pockets and its shallow angle of attack;
FIG. 9 is a sectional view of the impeller of FIG. 3 showing a
buildup of fines within its pocket and the path of travel of a rock
relative to an impeller;
FIG. 10 is a schematic top plan view of the turntable, its impellers
and the anvils of the rock crusher of FIG. 1 showing the outward
movement of rocks past the impellers and against the anvils.
BEST MODE OF CARRYING OUT THE INVENTION
Reference will now be made in detail to the preferred embodiments
of the invention, examples of which are illustrated in the accompanying
drawings. While the invention will be described in conjunction with
the preferred embodiments, it will be understood that the described
embodiments are not intended to limit the invention specifically
to those embodiments. On the contrary, the invention is intended
to cover alternatives, modifications and equivalents, which may
be included within the spirit and scope of the invention as defined
by the appended claims.
A rock crusher, generally designated 10 is shown schematically
in FIG. 1 and includes a cylindrical housing 12 with an open bottom
14 and a top that is closed by a feed device 16 and an annular lid
18. Feed device 16 includes a hopper 20 and a feed tube 22 that
are centrally positioned of lid 18. As shown in FIG. 1 hopper 20
and feed tube 22 introduce large size rocks 21 or other material
to be crushed, into the interior chamber 24 formed by cylindrical
housing 12.
At the center of interior chamber 24 is a round turntable 26 which
is rotatably supported by a bearing assembly 28. Turntable 26 is
positioned directly below feed tube 22 and in position to receive
rocks 21 from the feed tube. A suitable drive means 30 such as
a motor and pulley assembly, rotates turntable 26 at a desired RPM,
for example, 1000 to 2000 RPM.
A series of impeller blades or ejectors 34 are mounted in spaced
relationship about the outed periphery of the turntable. The design
of impeller blades 34 comprise an important aspect of the present
invention and is discussed in more detail with reference to FIGS.
3-10.
A ring of anvils 40 (only two anvils shown in FIG. 1) surround
turntable 26 and are vertically aligned with impellers 34. Anvils
40 are mounted to brackets 42 which in turn secure the anvils to
the side wall of housing 12. The operation of rock crusher 10 is
discussed in more detail with reference to FIG. 10.
Referring to FIG. 2 five impellers 34 are mounted to turntable
26. Impellers 34 are equally spaced and are mounted at the periphery
of turntable 26 at the edge of a feed cone 46. Feed cone 46 forms
the center region of turntable 26 and is formed as a slightly raised
conical member. The slope of conical feed cone 46 causes rocks to
be deflected outwardly into the path of travel of impellers 34 upon
dropping of rocks 21 onto the turntable. Feed cone 46 may or may
not be rotated with turntable 26.
It can also be seen in FIG. 2 that anvils 40 are angled to one
side. While only a pair of anvils 40 are shown on each side of housing
12 anvils 40 comprise a ring of anvils that surround turntable
26 as best seen in FIG. 10. Turntable 26 is shown in FIGS. 2 4
and 10 as rotating in a counterclockwise direction, as indicated
by arrow 27 which moves the impellers on an arcuate path, causing
the rocks to be propelled by the impellers with a counterclockwise
component of travel. Anvils 40 are angled so as to directly face
the outwardly traveling rocks. The angle of the anvils is shown
and discussed in more detail with reference to FIG. 10.
FIG. 3 shows the improved design of an impeller 34 of the present
invention. Impeller 34 is generally a wedge-shaped and rectangular
member having a narrow end 48 and a wide end 50. The back side 52
of impeller 34 is mounted to a bracket, discussed later, which in
turn secures the impeller to turntable 26. The front or forwardly
facing wear face 54 is the side of impeller 34 that contacts the
rocks. A curved, somewhat C-shaped pocket 56 is formed in front
side 54.
The present invention resides in the improved design of pocket
56. Accordingly the material of which impeller 34 is made can be
any conventional high strength, impact resistant material commonly
used for rock crusher impellers, most commonly, high-impact, abrasion-resistant,
cast white iron.
FIGS. 4-6 show the mounting brackets, generally designated 62
that secure impellers 34 to turntable 26. Each mounting bracket
62 includes an upright section 64 a large, outer gusset 66 and
a small, inner gusset 68. Each mounting bracket 62 also includes
a central opening 70 (FIG. 6) in upright section 64 which opening
is sized to closely receive a hub extension 72 of impeller 34. Hub
extension 72 includes an internally threaded passageway 74 which
threadably receives a headed bolt 76 to secure impeller 34 to bracket
62. A spacer washer 78 fits around hub extension 72 and a larger
mounting washer 80 is positioned between bolt 76 and bracket 62.
A compressible helicoil 82 screws into the cast threads of passageway
74 to provide a more uniform threaded fit with the machined threads
of bolt 76. It should be noted that the above-described mounting
arrangement for each impeller is exemplary and that other suitable
designs should be apparent to those skilled in the art, for example,
double helicoil systems and transverse pin-based systems.
FIG. 7 illustrates the angle of attack of wear surface 54 represented
by the included angle arrow 90 of an impeller 34. Angle of attack
90 is the angle between a radial line 92 and the front side 54 of
impeller 34. Radial line 92 represents a radial line of turntable
26 extending from the center of the turntable to the turntable's
outer edge 94. Each impeller of turntable 26 has an identical angle
of attack. As will be seen by comparison to the prior art impeller
of FIG. 8 it is an important feature of the impeller of the present
invention that it has an increased angle of attack 90. Impeller
34 is designed with a wedge shape that is more severe than prior
art impellers. Wide end 50 of impeller 34 is much wider or deeper
than prior art impellers. This creates a steeper angle for front
side 54 i.e., a greater angle of attack 90 which exposes pocket
56 more to oncoming rocks. Compare impeller 34 of the present invention,
as shown in FIG. 7 with a prior art impeller design shown in FIG.
8 and it will be seen that the angle of attack 90 is approximately
twice the angle of attack 104 for the prior art impeller.
FIG. 8 shows a prior art impeller 100 mounted on turntable 26.
Impeller 100 has a narrow, wide end 102 that is less than wide end
50 of impeller 34. Consequently, the angle of attack, included between
radius 92 and wear surface 117 and shown by arrow 104 of prior
art impeller 100 is significantly shallower than angle of attack
90 of impeller 34.
Impeller 34 is designed to be mounted on turntable 26 in the same
orientation of back surface 52 as is back surface 106 of prior art
impeller 100. Thus, the increased angle of attack 90 is preferably
achieved. It will be understood that impeller 34 also could be provided
with an increased angle of attack 90 by using a wedge shaped mounting
washer (not shown). It is desirable, however, to employ the existing
fixed mounting brackets 62 on rock crushers without having to use
special washers or having to change the angle at which mounting
brackets 62 are mounted to turntable 26. Both alternatives, however,
are deemed to be broadly within the scope of the present invention.
At the present time, using pocket configuration 56 an angle of
attack 90 of about 8 degrees has been found to be highly effective
in retaining fines in pocket 56. Prior art impeller 100 for example,
has an angle of attack 104 of 4 degrees. As angle 90 is increased
abrasion will increase, but greater angles are possible using pocket
configuration 56. Conversely, lesser angles of attack 90 are possible,
but there is some greater tendency to lose fines out of pocket 56
which tendency can be resisted to some degree by shaping the pocket
with an overhanging lip, which is described in more detail below.
FIG. 7 also illustrates the curved, C-shape of pocket 56 of the
impeller of the present invention. Pocket 56 extends from a shallow
end proximate end 48 of the impeller to a deepest end proximate
end wall 59 and forms a transversely extending lip 111 defining
the radially outermost edge of pocket 56. One advantage of a pocket
which gradually increases in depth from the radially inner end toward
the radially outer end is that rocks will impact the heel or innermost
portion of the pocket at an oblique angle, causing less abrasion.
Pocket 56 also is shaped with inner region 57 defined by concaved
end wall 59 which extends radially outwardly beyond an imaginary
line 113 that runs perpendicular to radial plane 92 and intersects
the leading edge of lip 111. In operation, fines 116 build up in
pocket 56 as rocks are impacted and thrown outwardly by the impeller.
The negative or radially outwardly sloping pocket surface or end
wall 59 below lip 111 helps trap fine 116 within the inner portion
or region 57 of pocket 56. Such fines have to move against centrifugal
forces on them, as well as against incoming rock and new fines in
order to get around lip 111 which only happens to a limited extent.
Thus, a collection of fines 116 always remains within pocket 56
which significantly improves the wear or abrasion resistance of
impeller 34. As will be seen, the greater angle of attack 90 works
in combination with the shape of pockets 56 to negatively or radially
inwardly incline pocket surface 59 and enhance the effectiveness
of lip 111 in retaining fines 116.
FIG. 8 illustrates the pocket design of prior art impeller 100.
Impeller 100 includes a pair of pockets 110 112 that are squared-off,
as compared to the inwardly curved shape of pocket 56 of impeller
34. Imaginary lines 115 115', like imaginary line 113 extend perpendicular
to radial plane 92 and intersect the bottom edges of pockets 110
112. The squared-off design and perpendicular orientation of pockets
110 112 allows a certain amount of fines carried by rocks to build
up within the pockets, as shown by broken lines 114 which indicates
the amount of fines in the pockets. However, the positive or forward
tilt of front walls 119 119' of the pockets results in the escape
of a significant amount of fines 114 which are simply forced by
centrifugal forces and incoming rocks and fines over outer edges
117 117' of pockets 110 112. The combination of a small angle
of attack 104 and the shape of pockets 110 and 112 makes it very
unreliable as to whether or not fines will remain in the impeller
pockets. The squared-off design of pockets 110 112 therefore,
works best for rock material having a high content of fines and
moisture. Due to the forward or outward slope of walls 119 119'
only a small quantity of fines 114 normally can build up within
the pockets and sometimes the pocket are swept clean. A substantial
quantity of fines constantly escapes from pockets 110 112 which
requires the rocks to carry with them enough fines to replace the
escaping fines and thereby maintain sufficient quantity of fines
within the pockets to minimize wear on the impeller blade. Fines
with high moisture content have greater capacity to stay within
the pockets and, thus, maintain the wear resistant surface provided
by the fines.
FIG. 9 illustrates the path of a rock 120 relative to an impeller
34 which is shown by arrow 126. As the rock is moving off of the
feed cone of the turntable and into the path of impeller 34 it
is traveling in the direction indicated by arrow 122 which approximates
a radial path from the turntable. As the rock moves into the path
of the impellers (which in FIGS. 7-9 are shown rotating in a clockwise
direction), the rock engages the impellers and are propelled clockwise
by the impeller. As the rock moves outward toward pocket 56 the
rock starts to move at least partially into the pocket, wherein
the rock helps to pack the fines into the base of the pocket under
lip 111. It is within the pocket region that the rock begins to
rapidly accelerate. Normally, the impact of the rock with the impeller
and its rapid change of direction and acceleration increases wear
on the impeller surface. However, provision of a pocket of fines
116 at this point creates a renewable wear surface that isolates
the impeller from abrasion. Radially outwardly or beyond the pocket
region, the rock is contacted by a convex surface 121. Surface 121
causes rock 120 to continue to rapidly pick up speed, causing the
impeller to act like a sling shot, hurling the rock outwardly off
of the impeller in the direction of arrow 126.
Since the fines 116 within pocket region 57 are impacted by oncoming
rock 120 and are also trapped by lip 111 rock 120 tends to compact
the fines into the pocket. This results in the escape of fewer fines
back into the stream of moving rocks. Consequently, impeller 34
works quite well with rocks having dry fine material, rocks having
a minimal amount of fines and larger and harder rocks, than does
prior art impeller 100.
The fines 116 provide a wear surface on the front side 54 of impeller
34 at the point where the rocks begin to rapidly pick up speed.
The outer layer of fines are generally swept away with oncoming
rocks, but subsequent fines land in the pocket and replace the escaping
fines, thereby maintaining an evenly distributed wear surface of
fines within the pocket. The fines deep within the inner portion
57 of pocket 56 remain trapped therein, thus ensuring a pocket of
fines for engaging oncoming rocks.
As best may be seen in FIGS. 3 and 9 impeller 34 of the present
invention further preferably has inwardly converging side walls,
flanges or rails 123 123' which extend radially along opposite
sides of wear surfaces 54 pockets 56 and convex wear surface 121.
Rails 123 123' project in a circumferential direction and tend
to catch rocks 120 and keep them from bouncing upwardly off the
turntable, as well as converging or collecting the rocks and fines
toward pocket 56. Such rails are broadly known in the prior art,
as seen in FIG. 8 but in impeller 34 of the present invention side
flanges or rails 123 123' are formed with a greater depth and are
formed to converge toward pocket 56.
As also may be seen in FIG. 3 impeller 34 may optionally be formed
with a relieved or upwardly sloped side 125 proximate small end
48. This configuration allows inner small diameter end 48 of the
impeller to be placed over the outer edge 127 of feed cone 46. Such
a construction is optional, but in some centrifugal rock crushers
feed cone 46 is held on turntable 26 by the inner ends 48 of impellers
34 for example, as shown in FIG. 10. Sloped or notched wall 125
allows the impellers to overlap the edge of the feed cone.
FIG. 10 illustrates operation of the rock crusher assembly. Rocks
120 land on feed cone 46 of turntable 26 and move radially outwardly,
as indicated by arrows 122 into the path of rotating impellers
34. As rocks 120 reach the pocket regions 56 of impellers 34 they
rapidly pick up speed and are propelled in a tangential direction,
as indicated by arrows 124.
Anvils 40 are lined up so that they are substantially normal to
direction of travel 124 of the oncoming rocks in order to create
a head-on impact. Upon impacting the anvils, the rocks break apart
into a multiplicity of small pieces, as indicated by arrows 130.
While the present invention has been described in connection with
a process for crushing "rocks," the present invention
is applicable to centrifugal crushing materials such as concrete,
cement clinkers, coal, sulfur, soda ash, salt, asphalt, precious
metal ores, as well as a wide range of rock aggregate. Consequently,
the present invention is not meant to be limited to rocks and where
the term "rocks" appears in the claims it is meant to
cover other types of material suitable for crushing or breaking
up. Also, in the claims the term "fines" is meant to cover
particulate material that is significantly smaller than the material
to be crushed or broken apart, and which particulate material is
capable of being packed within the impeller pocket described herein.
The method of the present invention provides a way of retaining
rock fines in the pocket of a pocket rock crusher impeller. In the
present method a radially outermost wall 59 of the impeller pocket
is oriented to tilt or slope radially inwardly to trap rock fine
116 against ejection from the pocket. Impeller 34 is secured in
the present method to the rock crusher turntable within wall 59
oriented in a slightly inwardly tilted orientation. This can be
accomplished by forming pocket 56 with a wall that will be inwardly
sloped when mounted to a standard turntable, or by providing a mounting
structure which orients wall 59 in an inwardly tilted orientation
by increasing the angle of attack 90 or both.
The present method insures that centrifugal force on the fines
tends to pack them in pocket 56 and that incoming rock further
resists fines escape from the pocket. This allows harder rock and
rock with fewer fines to be crushed using pocketed impellers, and
allows the pocketed impellers to have a longer wear life as a result
of using the fines as a replaceable wear surface.
The foregoing descriptions of specific embodiments of the present
invention have been presented for purposes of illustration and description.
They are not intended to be exhaustive or to limit the invention
to the precise forms disclosed, and obviously many modifications
and variations are possible in light of the above teaching. The
embodiments were chosen and described in order to best explain the
principles of the invention and its practical application, to thereby
enable others skilled in the art to best utilize the invention and
various embodiments with various modifications as are suited to
the particular use contemplated. It is intended that the scope of
the invention be defined by the Claims appended hereto when read
and interpreted according to accepted legal principles such as the
doctrine of equivalents and reversal of parts. |