Abstrict A centrifugal crusher having a rotor-crusher and a cylindrical
grate rotatably mounted about it, wherein the grate is made up from
a plurality of bars which on both sides having cam-shaped configuration
such that when the bars are assembled, the adjacently lying bars
form with their mating cams polygonal or circular apertures which
serve as the calibrating apertures for the grit. The bars on their
inwardly facing surfaces are formed at a roof-shaped angle to facilitate
the material handling capacity of the grate.
Claims Having thus described the invention, what I claim as new and desire
to be secured by Letters Patent, is as follows:
1. A rotatable grate means for a centrifugal crusher apparatus,
said grate means comprising a plurality of grate bars, each of said
grate bars having on opposite sides thereof cam means formed thereon,
said cam means having the configuration of one half of a circle,
wherein means are provided on said grate bars for assemblying adjacently
lying ones of said grate bars into a continuous cylindrical hollow
body forming said grate means, wherein said cam means of said adjacently
lying bars form a plurality of apertures, each of said apertures
having a predetermined conicity, said conicity having a larger dimension
lying in the direction of grit passage through said aperture, and
wherein a side of said grate bars lying in the direction of grit
passage through said apertures has formed thereon between adjacently
lying apertures roof-shaped projections for crushing and for guiding
the grit material toward the adjacently-lying apertures, each of
said projections running along the substantial length of the bar,
wherein said cam means are formed on one side of said bars in a
predetermined geometrical relationship with the cam means on the
otherside of said bars for allowing a predetermined distribution
of the apertures in each row with respect to the apertures in the
other row, when said bars are assembled into said grate means.
2. The grate means as claimed in claim 1 wherein said cam means
are formed on said bars symmetrically.
3. The grate means as claimed in claim 1 wherein said cam means
are formed on said bars offset on one side with respect to the cam
means on the other side.
Description FIELD OF THE INVENTION
The present invention relates to a centrifugal crusher having a
rotating grating member in it in general and, more particularly,
it relates to a centrifugal crusher which has a rotating grate provided
with grate bars which have a special structure to achieve the separating
of the grit according to a multidimensional size requirement.
BACKGROUND OF THE INVENTION
Centrifugal crushers having a rotary grate have already been well
known and, one of them is illustrated in Hungarian Patent No. 160238
which is incorporated hereinto by reference, as to the essential
parts and the environment in which a rotary crusher with a rotating
cylindrical grate operates. The crusher illustrated in the above-noted
Patent is being used mainly to perform grating or crushing assignments
in which the requirement is to produce a strictly defined upper
granular size for the grit and which also should have a uniform
granular structure.
It is also known that in centrifugal crushers having a rotary grate
the calibrating or separation of the grit is performed by the cylindrical
grate which is mounted for rotation about the striker-rotary member
and, which grate, at the same time, serves also as the impact surface
during the grating. This grate performs also the feeding of the
material to be grated in a continuous fashion onto the striker-rotary
member.
In order to satisfactorily perform the above-noted three major
required functions in practical applications, grates consisting
of bars turn out to be the best suitable because, in addition to
their good material feeding capability, they possess also sufficient
strength and rigidity. In addition, the grate bucket made up from
the bars can be repaired in a simple manner and the manufacturing
of the bars is relatively inexpensive and easy.
The grate bars used heretofore were similar to those used in hammer
mills. They are provided with an elongated slot between the bars
for purpose of separation of the grit and, the bars of such construction,
were able to perform a separation only in a single dimension, namely,
according to the thickness of the grit. In the case of hammer mills,
or such type of crushers, this was satisfactory because the maximum
size of the grit has been considerably smaller than the dimensions
of the slot between the bars. However, when it came to the application
of such structure to centrifugal crushers employing a rotating grate,
it was found that the thickness of a large quantity of the grits
will correspond to the dimensions of the slots because the striking
bars hit the grits in such a manner that they are impacted onto
the grate surface nearly in a vertical fashion, therefore, they
can easily pass through the slots of the grate. As a result the
grit will contain a large number of flat granules which have a thickness
which is satisfactory, however they will have a width which is much
greater than the width of the slot. Such granules can not pass through
a control sieve having rectangular meshes, therefore, they become
classified as excessive in dimension.
One may, therefore, conclude from the above, that the grates which
have been constructed with the heretofore known bars, cannot satisfactorily
meet stricter calibration requirements.
With such grates a desired upper grit size can be achieved only
if the slot between the bars is set to a considerably smaller dimension
than the maximum grit size. This would, however, considerably decrease
the passing capacity of the grate and also would decrease the uniformity
of the grit, because it would lead to an overgrating of the granules.
As a result, the quantity of the fractions which are close to the
dimensions of the slots would also be decreased due to the presence
of the large number of flat granules.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide
a rotary grate for a centrifugal crusher employing a bar construction
for the grate which is capable of cablibrating or separating the
grit according to a two dimensional requirement in size, namely,
including the dimension of the width and, at the same time, it possesses
a large passing capacity of the grit.
A basic principle of the invention rests on the recognition that
in the event of a two dimensional calibration or separation of the
grit, the largest calibrating or separating surface and the best
passing capability can be created by apertures which have the configuration
of regular polygon or circles, the latter actually representing
the extreme limit of the polygon. This stems from the recognition
that through a circular aperture a grit having a dimension which
is similar to the diameter of the aperture can pass in any position,
while in the case of a quadratic aperture it could pass only in
two positions, namely in those coinciding with the two diagonals.
Therefore, if the two kinds of apertures are capable of passing
similar grits having the same maximum size, then the circular aperture
will have a much larger probability of passing the grit than the
quadratic aperture. In other words, such granule will require the
more impacting onto the grate, in order to pass through it, the
less diagonals the aperture is having. Consequently, in the case
of centrifugal crushers having rotray grates, the inventive principle
recognizes that the circular apertures should be more advantageous.
It is also recognized, that for a similar separation requirement,
the diameter of the apertures in the grate having circular holes
can be 1.25 times the dimension of the apertures in a grate having
quadratic meshes. As a result, when the same number of holes are
given, the use of circular apertures in the grate, will result in
an available surface which is 22.7% greater than in the case of
quadratic apertures, which again will increase the passing capacity
of the grate.
In accordance with the invention, the rotary grate comprises grate
bars, the both sides of which are provided with cams which limit
or calibrate the width of the grit when the bars are assembled and
the adjacent grate bars are abutting each other. The space between
the cams correspond to the desired separating dimension and are
formed as the appropriately sized half polygon or half circles on
each bar when, in conjunction with the space formed in the adjacent
grate bar, will result in a regular polygon or in a circle and form
the sizing aperture.
In accordance with another aspect of the present invention, the
aperatures are constructed with a certain taper or increasing conicity
in the direction of the passing of the material in order to prevent
the sticking of the separated higher sized granules in the aperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more readily apparent from the
following description of a preferred embodiment thereof shown, by
way of example, in the accompanying drawings, in which:
FIG. 1 is a partial sectional view of the rotatary grate for a
centrifugal crusher according to the present invention provided
with the calibrating or separating aperatures;
FIG. 2 illustrates the rotatary grate according to FIG. 1 on its
inner surface, in a plan view;
FIG. 3 is a similar illustration as FIG. 2 of the same grate, except
from the upper surface thereof;
FIGS. 4 and 5 illustrate one of the grate bars in different views;
and
FIG. 6 illustrates in a sectional view a grate bar with a particular
intention to show the roof-like top surface.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to FIG. 1 it is seen that the rotary and cylindrical
grate bucket 1 has on its supports 2 a plurality of grate bars 3
mounted in a continuous fashion all along its cylindrical circumference
and which bars 3 are made from a high wear and abrasion resistant
steel material. On both sides of the grate bars 3 cams 4 are provided
which project out sideways and which as can be seen also in FIGS.
2 and 3 form in conjunction with the adjacent cams 4 of the neighboring
bars, when assembled as in FIGS. 1 and 2 the calibrating apertures
6 and also serve for the spacing of the bars. The reference character
5 in FIGS. 1 4-6 identifies a spacing cam at the lower side of
each bar 3 which further enhances the alignment of the outer end
portions of the bars which otherwise would be aligned and abutt
only through the cams 4.
The adjacently lying cams 4 after being rounded out form the series
of apertures 6 performing the calibration or separation of the grit.
The apertures 6 increase outwardly in a conical fashion, that is,
in the direction of the passing of the grated material in order
to aid the passing of the grits therethrough.
In order to increase the material feeding capability of the grate,
the inner surface of the grate bars which comes into contact with
the material, are formed by two planes intersecting in a roof-like
fashion as can be seen in FIG. 6 and, the resulting edge 7 will
increase the material feeding capacity of the grate 1.
The grate 1 according to the present invention, has its primary
advantage in that it can produce a perfectly calibrated or dimensioned
uniform grit with the centrifugal crusher into which the grate is
built into.
It is within the scope of the present invention that the apertures
6 can be symmetrically spaced in parallel rows over the grate or
offset with respect to each other. The latter situation requires
the asymmetrical camming of the two sides of a single bar and mating
it with a similarly cammed bar as in FIG. 5.
Further advantage of the present invention resides in that due
to polygon shaped or circularly shaped apertures 6 the grits which
already have the desired dimensions can quickly leave the crushing
space and, consequently, they will not undergo an additional and
unnecessary crushing. Despite the fact that the grate 1 according
to the present invention has a large passing capacity, it still
retains the strict calibrating qualities and, at the same time,
it retains a very high efficiency. When the striker rotor is appropriately
selected to have a certain perpherial velocity, the rotary grate
according to the present invention, when used in the crusher designed
accordingly, will be an excellent producer of coarse fractures or
granules which are required to be produced in very large quantities.
Also the rotary grate 1 according to the present invention due
to the inventive joining of the grate bars 4 will have a very rigid,
strong and reliably operating, longlasting construction.
I wish to be understood that I do not desire to be limited to the
exact details of construction shown and described, for obvious modifications
will occur to a person skilled in the art.
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