Abstrict A rotary impact crusher is characterized by a continuous rotary
circumference formed by a plurality of plates along the orbit of
rotation described by the crusher impeller blades and extending
from each impeller blade to each next blade. The impeller blades
are secured to the crusher body by a combination wedge means comprising
a truncated, thick walled cylinder and a polyhedron with matching
inclined planes. Both the plates and the impeller blades are symmetrical
in shape, and combination wedge means is located at a point of least
stress to each impeller blade.
Claims What is claimed is:
1. A rotary impact crusher impeller having a drive shaft, two spaced
shaft plates mounted on the shaft and extending radially outwardly
of the shaft, impeller blade recess in the periphery of each shaft
plate, a plurality of impeller blades spaced around the periphery
of each shaft plate with each blade extending through an impeller
blade recess in each shaft plate and the longitudinal axis of the
blade generally parallel to the axis of the rotary shaft, wherein
the improvement comprises a plurality of peripheral plates each
having a radial inner surface, each peripheral plate overlying the
opening between two adjacent impeller blades and the spaced shaft
plates, the radial inner surfaces of the peripheral plates resting
upon the outer peripheral surfaces of the shaft plates between the
adjacent impeller blades, a mounting member on the radial inner
surface of each peripheral plate and removable mounting means engageable
with the mounting members for securing the peripheral plates to
the impeller against centrifugal forces wherein the impeller blades
and peripheral plates form an essentially continuous surface extending
around the impeller for preventing work from falling into the impeller
interior during low-speed crushing.
2. An impeller as in claim 1 including a bar extending between
the shaft plates at each side of aligned pairs of impeller blade
recesses, the radial inner surfaces of the peripheral plates overlying
outwardly facing edges of said bars so as to support the peripheral
plates between the shaft plates.
3. An impeller as in claim 2 wherein the peripheral outer surfaces
of the shaft plates between adjacent impeller blade recesses and
the outer facing surfaces of the bars are all planar and the radial
inner surfaces of the peripheral plates are planar adjacent such
surfaces to permit flush mounting of the peripheral plates on the
impeller.
4. An impeller as in claim 2 wherein said bars include radially
outwardly facing impeller blade supporting surfaces engaging inwardly
facing impeller blade surfaces, the impeller is adapted for rotation
in a given direction about the axis of the drive shaft so that the
impeller blades have leading and trailing edges and including clamp
means for securing each impeller blade to a shaft plate, such clamp
means being located radially inwardly of the trailing edge of the
impeller blade, and an impeller blade support surface in each recess
located radially inwardly of the leading edge of each impeller blade.
5. An impeller as in claim 1 wherein the mounting member includes
an eye and said mounting means including a mounting shaft extending
through the eye and into a bore in at least one of said shaft plates.
6. An impeller as in claim 1 wherein said mounting member comprises
a pair of eyes extending radially inwardly from the inner surface
of the plate adjacent the shaft plates, bores extending through
the shaft plates and including an attachment shaft extending through
said bores and eyes for holding the peripheral plate to the impeller.
Description In crushing or pulverizing, materials such as stone, coal, slag
or the like are reduced to a suitable size for uses such as road
building, concrete aggregate and furnace firing. The reduction in
size may be accomplished by compression, which is the slow application
of a large force; impact, a rapid blow as by a hammer; attrition,
a rubbing or shearing; or by a combination of these techniques.
The present invention relates to a rotary disintegrator such as
a rock crusher or hammermill. Prior crusher devices have been described
in U.S. Pat. No. 3480214 and U.S. Pat. No. 3608841 relating
to rotary disintegrators, such as rock crushers, having a housing
with an inlet for feed material, an impeller rotatable around a
horizontal axis and provided with at least one axially extending
impeller blade projecting outwardly of the impeller. The material
to be crushed is admitted from above into the impact chamber so
that it falls onto and is impacted by the impeller blades. Material
which is impacted by the impeller blades is flung against plates
that line the housing. Repeated impacting of the material by the
blades and the plates causes the crushing of the material. In theory,
force is applied to the material in the form of blows and impacts
until the cohesion of the material collapses. The energy to break
the material is applied at high speed in the form of kinetic energy.
This type crusher employs no significant amount of other kinds of
crushing actions such as attrition, shearing and/or compression.
Devices of this general nature are advantageous in that they are
characterized by a relatively high capacity for treating materials
related to power consumption and further by a high reduction ratio.
These devices are capable of comminuting fairly large materials
to discharges of relatively fine product. In order to achieve the
advantages of the rotary disintegrators described here, it is necessary
to maintain a high rotor speed in a range of 600 to 1500 revolutions
per minute--or in terms relating to conventionally sized crushers--6000
to 15000 feet per minute of impact speed. The higher the reduction
ration intended, i.e. the finer the product desired, the faster
the rotor must be operated. Operation at these high speeds causes
certain problems including accelerated wear of breaker blades and
plates, and the production of dust. Production of dust is disadvantageous
because of the waste of material and the development of dust control
problems. To a degree, the prior art crushers reduce these problems.
U.S. Pat. No. 3480214 specifically relates to a rotary disintegrator
provided with a pair of swingable grates disposed below the rotor
with a curvature approximating that of the blade orbit--the two
grates being separated from each other by a small gap at the nadir
of the rotor and forming two independently adjustable clearances
for the materials to be comminuted. The second grate may have its
entrance edge disposed slightly below the level of the discharge
edge of the first grate to intercept larger fragments accelerated
across the gap; above the exit of the ascending clearance formed
between the rotor and the second grate, a deflector plate intercepts
particles not previously discharged.
U.S. Pat. No. 3608841 relates to a rotary disintegrator provided
with one arcuate baffle extending beneath the impeller and along
an arc segment of approximately 90 degrees. This device provides
improved product control by decreasing the amount of oversize by
means of the pivotal, cylindrical, concave baffle which is provided
along a segment of the rotor orbit. Further, this baffle may be
movable so that the impeller blade wear may be compensated for by
adjusting the concave baffle in the direction of the rotor orbit.
In operation, it is an objective of the prior art crushers and
similar devices, to minimize impeller blade wear while maximizing
product size control. These objectives work against one another.
Thus, reducing the speed of the rotor decreases wear, however, this
results in loss of product size control. The present invention addresses
itself to those objectives as well as to others. It relates specifically
to crushing devices of the type disclosed in the cited patents and
has general applicability to rotary impact disintegrators as described.
It is proposed by the present invention to provide a rotary disintegrator
capable of operating at lower speeds than those necessary in either
conventional impact crushers or those utilizing the features of
the prior art devices. A device is provided that permits disintegration
at lower speeds, thus preventing over-crushing of large size feed,
reducing wear on equipment and minimizing dust production. The invention
is describable as a rotary impact crusher comprising an impeller,
rotatable about a horizontal axis and provided with at least four
axially extending impeller blades mounted on the circumference of
the impeller and a plurality of peripheral plates mounted on the
circumference of the impeller between the blades to provide the
impeller with a continuous rotary circumference along the orbit
of rotation described by the impellers while in rotation. One plate
extends from each impeller blade to each next impeller blade to
close the circumferential spaces between the blades. This structure
permits the operation of impact crushers at lower speeds than those
previously used bringing about the advantages as already described.
Devices already known in the art could not be operated at these
lower speeds because material would overcome the centrifugal force
imposed by impeller velocity and would penetrate into the rotor
to cause damage, clogging and at least a decrease in the efficiency
of the comminuting action. The present invention is particularly
applicable to a device of the type shown in the cited patents since
there the problem of material penetration into the rotor area is
compounded by use of the curved grate.
Another aspect of the present invention relates to a combination
wedge means for securing the replaceable impeller blades to the
impeller. This wedge means comprises a truncated, thick walled cylinder
and a polyhedron characterized by a plane to cooperate with the
plane formed by the truncation of the cylinder, and a lip to loosely
engage a rim of an impeller blade formed by a notch beneath the
lower shoulder of the blade.
The combination wedge for each blade is positioned at a peripheral
recess in the shaft plates extending from the rotary axis. The wedge
is aligned with a recess in each impeller blade at a following lower
edge--a point of minimum stress. A slanted plane of the cylinder
cooperates and presses against a corresponding surface of the polyhedron.
The polyhedron fits within the recess of the blade. A plane of the
polyhedron is urged against the body of the blade while the lip
of the polyhedron rests within the recess and in operation "catches"
the edge of the recess to provide a removable but secure fitting.
This double wedge combination is particularly advantageous because
it is accessable for removal or adjustment even with the peripheral
plates of the present invention.
Another aspect of the present invention, illustrated in the drawings,
is the symmetrical shape of the impellers and peripheral plates.
This permits these elements to be removed and turned to a new work
position whenever a blade edge or plane is worn to the point of
adversely affecting operation. In a preferred embodiment, the impact
crusher has symmetrically shaped impeller blades having an upper
leading and an upper following edge and a lower leading and lower
following edge extending outwardly to form four arms and shoulders.
Other objects and features of the invention will become apparent
as the description proceeds, especially when taken in conjunction
with the accompanying drawings illustrating the invention, of which
there are six sheets and two embodiments.
FIG. 1 is a cross-sectional view of an impact crusher embodying
the present improvements;
FIG. 2 is a detailed view of a section of the crusher of FIG. 1
showing two impeller blades and adjoining peripheral plate;
FIG. 3 is a sectional view taken on the line A--A of FIG. 2;
FIG. 4 is an isometric view of the two parts of the combination
wedge means for supporting the replaceable impeller blades;
FIG. 5 is a sectional view of the combination wedge means showing
the cooperation of planes of the two parts;
FIG. 6 is a view of a section of the crusher showing another embodiment
of the intervening plate; and
FIG. 7 is a sectional view taken on line B--B of FIG. 6.
Referring to FIG. 1 the rotary crusher 10 has a housing 11 with
a pivotal top 11a and pivotal doors 11b and 11c. Rock or the like
is loaded into the feed opening 12 toward the turning impeller 13.
The impeller 13 spins in a counter-clockwise direction as it is
depicted in FIG. 1. As it turns, it flings rock feed against a series
of breaker plates 14. This effectively smashes the larger fragments.
The feed is then conveyed by the impeller 13 down toward baffle
15. At this point the clearance between the orbit of the impeller
13 and the baffle 15 may be adjusted by screw and spring arrangement
17 which operates to pivot the baffle 15 at shaft 16 to reduce the
gap 18 between the rotor orbit and baffle 15. Adjustment of the
clearance between the baffle 15 and rotor orbit can be utilized
to affect the size of the product. As the partially fragmented rock
is carried around against the baffle 15 by the impeller 13 it is
fully milled and reduced to desired size. The feed is then projected
in the form of a hail of particles against the lining 19 of the
door 11c and then discharged from the bottom 20 of the crusher.
Referring to FIGS. 2 and 3 the exemplary impeller arrangement
shown is characterized by two shaft plates 21 rotatable with drive
shaft 22 (shown in FIG. 1) and radially extending outwardly from
said shaft. The plates 21 include a plurality of aligned peripheral
recesses 23 the recesses in the two plates being aligned axially
of each other to receive impeller blades 25. Bars 24 are welded
between the plates 21 on either side of the recesses, to support
impeller blades 25 and peripheral plates 26. Plates 26 cover adjacent
spacing between the blades 25 to form a continuous circumferential
surface along the impeller orbit. This structure prevents the incursion
of feed material into the impeller 13 while being operated at low
speeds.
Each plate 26 rests on flat surfaces 27 of shaft plates 21 and
is provided with at least two attaching eyes 26a. A shaft 28 extends
through eyes 26a and holes 29 in plates 21 to secure plates 26 against
centrifugal force while the impeller 13 is in operation. Shaft 28
is held in place by means of pins 30 one on the outside of each
plate 21 and mounted in holes 31 in the shaft 28. The shaft plates
21 support blade 25 at surface 32. The plate 26 is supported by
the shaft plates 21 at the point of attachment, i.e. the hinge eyes,
thus minimizing wear at a critical attachment point and permitting
conventional attachments since the hinge attachment acts only to
resist centrifugal force. Because of the support of the plate at
bars 24 force of the feed against the plate is resisted. In the
embodiment shown, the plate rests partially on bars 24 and partially
on the surfaces 27. In another embodiment the plate may rest solely
on a bar 24 bearing no weight or force on surfaces 27. This latter
embodiment is illustrated in FIG. 6 and in FIG. 7. As shown in FIG.
6 plate 26 is supported by bars 24 which are welded between and
bridge shaft plates 21. The angle between the bars 24 and the adjacent
flanks of plate 26 should be between 60 and 180 degrees. Also, the
angle between bar 24 and the blade 25 is supports should be between
45 and 90 degrees to the radius of the rotor.
As indicated, the present invention utilizes symmetrical pieces
in order to provide one of the advantages as described. Plate 26
illustrates this principle. Further, as shown, impeller blade 25
is symmetrically shaped with four like edges 25a. The blade 25 preferably
is symmetrical, to either side of a radial plane so that it may
be reversed more than once as wear occurs. Hence, as one leading
edge 25a becomes worn, the blade may be reversed to expose a fresh
leading edge to the feed.
The impeller blade shown has a narrow waist and four bevelled shoulders
25b, 25c, 25d and 25e which form an angle of between 35 and 60 degrees
with the radius of the impeller 13. While in operation, the shoulders
25b, 25c, and 25d of the impeller blade 25 are subjected to the
greatest stress from feed impact and the crushing operation. In
accord with another aspect of this invention, the blade 25 is supported
at these surfaces. Hence, the drawings show outwardly facing bars
24 under blade shoulders 25b and c and inwardly facing support surface
32 of plates 21 supporting the outward facing shoulder 25d.
A combination wedge means 35 is positioned at the point of lowest
stress 25e located radially inwardly of the trailing edge of each
blade 25. The means consists of a cylindrical wedge 33 and polyhedron
34. The slanted surface 33a cooperates and presses against the corresponding
surface 34a of polyhedron 34. The polyhedron 34 fits within the
recess 25f provided in the blade shoulder 25e. The wedge 33 fits
in cylindrical recess 36 formed in one side of larger plate recess
23 opposite impeller blade recess 25f. The plane 34b of the polyhedron
is urged against the body of the blade 25 while the lip 34c of the
polyhedron rests within recess 25f and in operation "catches"
the edge of recess 25f to provide a removable but secure fitting.
Truncated cylinder 33 is engaged within recess 36 in body 21. Its
slanted surface 33a cooperates with the surface 34a of polyhedron
34 to lock the impeller blade in position. In its secured position
the cylinder is biased outward by the constriction of the recess
and against the polyhedron 34. This provides a secure and firm fitting
while at the same time permits the polyhedron to loosely engage
the edge of recess 25f. Truncated cylinder 33 further may be secured
by means of a bar (not shown) through its axial bore 33b.
While I have illustrated and described a preferred embodiment of
my invention, it is understood that this is capable of modification,
and I therefore do not wish to be limited to the precise details
set forth, but desire to avail myself of such changes and alterations
as fall within the purview of the following claims. |