Abstrict A jet air flow crusher has a guide face formed by the inside surface
of an outer wall in which a flat and almost ellipsoidal internal
space is defined to guide an ellipsoidal gas phase flow powder grains;
a crushing zone in which flowing powder grains are crushed provided
on one side of the internal space in the direction of the ellipsoidal
major axis; a classifying zone at which flowing powder grains are
discharged provided on the other side of the internal space in the
direction of the ellipsoidal major axis; a gas phase flow passage
defined in the crushing zone by the inside surface of the outer
wall and a partition wall; nozzles installed in the outer wall and
the partition wall at several locations in the direction of the
powder grain flow in the crushing zone to jet out air in a direction
substantially corresponding to the powder grain flow for carrying
and crushing the powder grains, and flow resisting means for limiting
the gas phase flow carrying the powder grains, arranged at least
at one location between the nozzles spaced from one another in the
direction of the powder grain flow.
Claims What is claimed is:
1. A jet air flow crusher for crushing powder grains, said crusher
comprising:
an outer wall in which an internal space is defined;
powder grain introducing means open to said internal space for
introducing powder grains therein;
a partition wall within said outer wall, said partition wall partitioning
said internal space into a crushing zone and a classifying zone
open to said crushing zone,
said crushing zone defined and extending in a powder flow direction
between an outer guide surface of said partition wall and an internal
surface of said outer wall,
said classifying zone comprising an outlet through which crushed
powder grains are discharged from said internal space;
a plurality of nozzles open to said crushing zone, said nozzles
spaced apart and directed in said powder flow direction, and said
nozzles connectable to a source of compressed air for jetting air
into said crushing zone in substantially said powder flow direction
to cause the powder grains to be crushed in said crushing zone and
to carry the powder grains from said crushing zone toward said classifying
zone; and
flow resisting means disposed in said crushing zone between respective
ones of said plurality of nozzles for inhibiting the flow of powder
grains in said powder flow direction from one of said respective
ones of said plurality of nozzles to the other of said respective
ones of said plurality of nozzles whereby powder grains accrue in
the crushing zone at said flow resisting means prior to flowing
to said other of said respective ones of said plurality of nozzles,
said flow resisting means comprising nozzle means open to said
crushing zone at a location between said respective ones of said
plurality of nozzles, directed perpendicular to said powder flow
direction, and connectable to a source of compressed air flow for
directing a jet of air into said crushing zone in a direction perpendicular
to said powder flow direction, and
said other of said respective ones of said plurality of nozzles
disposed, in said powder flow direction, between said flow resisting
means and said classifying zone.
2. A jet air flow crusher for crushing powder grains as claimed
in claim 4
wherein said outer wall has an elliptical inner surface whereby
said internal space is ellipsoidal, said crushing zone being defined
on one side of said internal space in a direction corresponding
to a major axis of said ellipsoidal inner space, and said classifying
zone being defined on the other side of said ellipsoidal internal
space.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a jet air flow crusher, and particularly
to a jet air flow crusher which can crush, break or grind powder
grains by using jet air flows.
1. Description of the Related Art
Conventionally, jet air flow crushers have been widely used, because
they are easier to maintain and operate than other types of crushers
and they are very adaptable to air flow classifiers to which they
are connected.
Furthermore, they have been considered to be very useful for crushing
various types of powder having a low heat resistance (for example,
plastic powder), because they do not produce any significant heat
during their operation. These jet air flow crushers have been used
not only to crush various types of powder in a narrow sense, but
also to break any agglomerate of powder grains, or to remove foreign
matters sticking to the surfaces of powder grains.
Various types of jet air flow crushers have been known such as
those wherein nozzles are installed, for example, in a cylindrical
wall to jet air from the cylindrical wall in an inward and tangential
direction so as to direct the powder grains with the jet air along
the inside surface of the cylindrical wall and to cause collisions
between the powder grains (hereinafter referred to as "turning
flow type"), wherein nozzles to jet air to carry powder grains
are inwardly opposed to each other so as to enhance the collision
force between powder grains (hereinafter referred to as "opposed
crushing nozzle type"), wherein jet air to carry powder grains
is blown against the surface of a hard wall (hereinafter referred
to as "object collision type"), and wherein jet air is
blown out through the partial wall of a gas phase flowing passage
in the form of an ellipse and carry powder grains in the gas phase
flowing passage so as to cause collisions between powder grains
for crushing them (hereinafter referred to as "jet O-mizer"
type).
However, these types of crushers devised or practically used have
prevented several problems to solve.
For example, the "turning flow" type crushers, though
applicable to the crushing processes for very small quantities of
powder, present a disadvantage in that due to the construction of
the mechanism to remove crushed particles from the center part of
the turning air flow (generally called "classifying mechanism"),
an equivalent quantity of large-sized or coarse particles is also
removed with fine particles, and thus they do not possesses a sufficient
industrial processing capacity. The "opposed crushing nozzle"
type crushers present problems is that they are effective on only
10 .mu.m or more powder particles between which collisions take
place. The "object collision" type crushers also present
problems with respect to durability and contamination of foreign
matter, because they cause wear of the wall against which the powder
grains strike.
The "jet O-mizer" type crushers which can be provided
with any apparatus for efficiently removing crushed powder particles
having a uniform distribution of grain sizes. However, this type
of crusher offers a problem in that it cannot sufficiently provide
fine sizes of crushed powder grains thereby having a limitation
in its applications.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate various problems
presented by the conventional jet air flow crushers as described
above.
Another object of the present invention is to provide a jet air
flow crusher which can efficiently produce powder particles having
a size of approximately 10 .mu.m or less.
A further object of the present invention is to provide a jet air
flow crusher which is small, has a simple construction and operates
very well.
The jet air flow crusher according to the present invention comprises
a guide face formed by the inside surface of an outer wall in which
a flat and almost ellipsoidal internal space is defined to guide
an ellipsoidal gas phase flow carrying powder grains; a crushing
zone in which flowing powder grains are crushed provided on one
side of the internal space in the direction of the ellipsoidal major
axis; a classifying zone at which flowing powder grains are discharged
on the other side of the internal space in the direction of the
ellipsoidal major axis; a gas phase flow passage defined, in the
crushing zone, by the inside furnace of the outer wall and a partition
wall, and nozzles installed in the outer wall and the partition
wall at several locations in the direction of the powder grain flow
in the crushing zone to jet out air in a direction substantially
corresponding to the powder grain flow for carrying and crushing
the powder grains, and is characterized by the fact that in the
crushing zone, a flow resisting means to limit the gas phase flow
carrying the powder grains is also installed at least at one location
between the nozzles spaced from one another in the direction of
the powder grain flow.
The inventors have developed the present invention for the following
reasons.
To provide such a type of jet air flow crusher to crush powder
grains carried in a gas phase flow, it has been desired to effectively
satisfy the requirements of crushing powder grains efficiently with
a great crushing force in the crushing zone and separating and removing
fine grains in a mixture of small and large powder grains in the
classifying zone. To embody the requirements of the crusher, it
has been desirable and possible to employ a crushing zone in which
the fluidity of powder grains is limited to cause the powder grains
to remain as long as possible and a classifying zone in which the
fluidity of powder grains is sufficiently increased to improve the
classifying effect on the powder grains involved in the gas phase
flow. Thus, the present invention has been devised by the inventors.
Therefore, the present invention comprises a flow resisting means
which limits the fluidity of powder grains in the crushing zone,
and a means which increases the fluidity of powder grains in the
classifying zone (hereinafter referred to as "fluidity amplifying
means"). The fluidity amplifying means is often and preferably
composed of, for example, the means which blows in air to increase
and amplify the fluidity of powder grains between the crushing zone
and the classifying zone which are separately defined on opposite
sides of the space defined by an almost ellipsoidal partition wall.
In the crusher according to the present invention, the flow resisting
means which limits the fluidity of powder grains in the crushing
zone functions as a weir against the powder grains carried in the
gas phase flow. Specifically, the flow resisting means may be preferably
a means which limits a flow passage mechanically and structurally
(or a throttle means), or a means which inhibits the flow of a gas
phase carrying powder grains by blowing air into the gas phase carrying
powder grains in a direction almost perpendicular to the gas phase.
The postion and direction in which powder grains are loaded into
the crusher thus constructed may be set properly so that the powder
grains will be able to flow in and together with the almost ellipsoidal
gas phase flow. In general, it is often desirable that a powder
loading inlet be placed in the passage where powder grains flow
from the classifying zone to the crushing zone. However, the present
invention is not limited to such.
According to the present invention, the casing which defines an
internal space in which powder grains flow to be crushed and classified
is almost an ellipsoidal. It is understood that the casing need
not have the shape of an ellipsoid in the strict sense.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1(a) is a plan view partially cross-sectional, illustrating
the jet air flow crusher according to the present invention.
FIG. 1(b) is a front sectional view of the crusher.
FIG. 2 is a front view of the crusher.
FIG. 3 is a plan view of the crusher.
FIG. 4 is a schematic view illustrating the flow of powder grains
in the crusher.
FIGS. 5(a) to 5(c) are partial sectional views illustrating the
flow of powder grains in parts of the crusher.
FIG. 6 is a graph showing the results of testing the crusher.
FIGS. 7 and 8 are partial plan views of jet air flow crushers according
to other embodiments of the present invention, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described below by referring to the
drawings annexed hereto.
FIGS. 1(a) and 1(b) illustrate an embodiment of a jet air flow
crusher according to the present invention. In this figure, 1 designates
internal space in which powder grains are carried in a gas phase
flow.
The internal space 1 is almost horizontal, has a flat ellipsoid
shape, and is confined impermeably by an outer gas phase flow guide
wall 5 (hereinafter referred to as "outer wall") which
defines the ellipsoidal space 1 and forms the passage of powder
grain flow with a bottom plate 13 and a top cover 10. Two seal rings
11 and 12 perfect the impermeable confinement of the internal space
1.
In the internal space 1 a central partition block 6 is formed
as shown in the figure to contribute to separating a crushing zone
2 and a classifying zone 3 from each other and defining the two
zones in preferred forms. In the crushing zone 2 the central partition
block 6 has an internal gas phase flow guide wall 60 extending parallel
to the outer wall 5. A gas phase flow passage 4b in which powder
grains are carried in a gas phase flow is defined by the internal
gas phase flow guide wall 60 and the outer wall 5. In the classifying
zone, the central partition block 6 has an internal turning flow
guide wall 61 for a classifying mechanism which removes fine powder
grains in the turning flow at its center part.
Between the crushing zone 2 and the classifying zone 3 the outer
wall 5 and the central partition block 6 define two other gas phase
flow passages 4a and 4c.
Outside the internal space 1 enclosed by the outer wall 5 a compressed
air chamber 7 is provided which is isolated with respect to pressure
from external space 1 by the partition bottom plate 13 the outer
wall 5 and the central partition block 6 and from the exterior
by a pressure chamber casing 14.
The compressed air chamber 7 is connected to an external compressed-air
source (not shown), for example, an air compressor, through a compressed
air pipe 21 connected to a compressed air intake 20 and open the
internal space 1 through air flow jet nozzles 50a to 50e as described
hereinafter so as to introduce compressed air into the internal
space 1.
The compressed air chamber 7 is also connected to another compressed
air chamber 8 in the central partition block 6 through a penetrating
hole 9 so that compressed air may be blown into the internal space
1 through jet air flow nozzles 50f as described hereinafter.
The powder loading mechanism in the crusher according to this embodiment
is constructed as shown in FIGS. 1(a), 2 and 5(a). At the location
at which the classifying zone 3 is connected to the gas phase flow
passage 4a, a powder jet nozzle 40 is provided which has an outside
end connected to the compressed air chamber 7 and an inside end
connected to the gas phase flow passage 4a. The central top part
of the powder jet nozzle 40 is connected with the lower end outlet
41 of a powder supply hopper 42 mounted on the top part of the top
cover body 10 so that the powder supplied by the hopper 42 can be
blown into the internal space 1 under of an ejector effect, while
compressed air is blown from the compressed air chamber 7 into the
internal space 1 through the nozzle 40. A diffuser 43 is disposed
in the internal passage of the nozzle 40.
The powder supplied by the hopper 42 is jetted by the nozzle 40
into the gas phase flow passage 4a in the longitudinal direction
as shown in FIG. 1(a).
As shown in FIG. 2 legs 15 support the pressure chamber casing
14. Except for the legs 15 all the components of the crusher are
generally made of a slick-surface-finished material such as stainless
steel. Ceramic material may be used when powder grains having a
higher abrasiveness are to be crushed.
FIG. 4 illustrates the flow of powder grains in the internal space
1. The specifics of the crushing zone 2 and the classifying zone
3 will be described below by referring to FIG. 4.
In this embodiment, the crushing zone 2 is constructed as shown
in FIG. 1(a). Along the gas phase flow passages 4a to 4c in the
form of an arc in which powder grains are carried in a gas phase
flow, the first to fourth air jet nozzles 50a to 50d, which blow
jet air into the passages 4a to 4c approximately in the direction
of the flow of powder grains and carrier gas, are disposed in the
outer wall 5 at a predetermined spacing. Each of these nozzles 50a
to 50d has an outside end facing the compressed air chamber 7 and
an inside end facing the gas phase flow passage 4b or 4c so that
compressed air is jetted from the compressed air chamber 7 into
the gas phase flow passage 4b or 4c through each of the nozzles
50a to 50d.
In each of these nozzles 50a to 50d as in the powder jet nozzle
40 is a diffuser which adjusts the velocity of the compressed air
jet so that flowing powder grains will be effectively crushed by
collisions therebetween caused by the air jetted out by the nozzles
50a to 50d in the directions described above. FIG. 5(b) shows the
conditions in which powder grains in the jet air flow collide against
each other.
This embodiment is characterized by the fact that in addition to
the first to fourth jet air flow nozzles 50a to 50d, fifth and sixth
jet air flow nozzles 50e and 50f are provided between the second
and third jet air flow nozzles 50b and 50c and face each other at
both sides of the gas phase flow passage 4b at such a setting angle
that the air jetted out by the nozzles 50e and 50f flows approximately
perpendicular to the longitudinal axis of the gas phase flow passage
4b.
The fifth and sixth jet air flow nozzles 50e and 50f are substantially
identical construction to the other nozzles 50a to 50d, but let
air in different air jet directions relative to the gas phase flow
passage 4b from the compressed air chamber 7 into the gas phase
flow passage 4b than do the latter.
Because the air jets from the fifth and sixth jet air flow nozzles
50e and 50f act as a type of weir (hereinafter referred to as "air
flow weir"), the powder grains carried by the gas phase flow
receive a resistance to their fluidity in the gas phase flow passage
4b so that they remain longer at the upstream position (on the side
of the nozzles 50a and 50b) than they would if there were no air
jets from the nozzles 50e and 50f. Therefore, the air jetted out
from the nozzles 50e and 50f increase the opportunities for powder
grains in the air jetted out by the nozzles 50a to 50b and clash
against each other, and thus improve the crushing efficiency of
the crusher according to the present invention.
The flow rate of jet air required to form the air flow weir may
be controlled by changing the diffusers in the nozzles, or by regulating
the pressure in each nozzle if an independent air source is used
for each nozzle. The flow rate of jet air for the air flow weir
depends upon the type and flow rate of powder to be processed. In
general, it is often desirable that the flow rate of jet air from
the nozzle 50f be set approximately 1/3 to 3/2 the flow rate of
jet air from the nozzle 50a.
On the downstream side of the air flow weir formed by the air jetted
from the nozzles 50e and 50f, the air jetted from the jet air flow
nozzles 50c and 50d provides opportunities at which powder grains
may be crushed and again amplify the fluidity of the gas phase flow
limited temporarily by the air flow weir so as to assure an effective
classifying process in the classifying zone.
In this embodiment, the classifying zone 3 is constructed so that
the powder grains introduced in the internal space 1 and carried
into the classifying zone 3 through the crushing zone 2 will turn
and flow along the outer wall 5 and the internal turning flow guide
wall 61 and that the fine powder grains produced are discharged
by the positive pressure in the internal space 1 to the exterior
through the powder outlet 30 formed in the top cover 10 in the center
part of the classifying zone 3.
In FIGS. 2 and 3 31 designates an outtake pipe for fine powder
grains, which is fixed on the top cover 10 through a flange 32 connected
to the outtake pipe 31 and connected to a proper air flow type
powder classifier disposed in the next process line.
The principle of the process of classifying and removing fine powder
grains by using a turning flow method has been conventionally known
wherein among the powder grains crushed, only the fine powder grains
having small sizes are selectively removed based upon the relationship
between the carrying force of the gas phase flow and the centrifugal
force acting on the powder grains. To apply a classifying and taking-out
mechanism based upon this principle to the crusher according to
the present invention, this embodiment is characteristically designed
so that the construction of the crusher can embody such a principle
so as to improve the classifying efficiency.
Particularly, the crusher in this embodiment comprises nozzles
(a powder jet nozzle 40 and a fourth jet air flow nozzle 50d) which
are placed at the upstream end positions along the gas phase flow
passages 4a and 4c, forming the linear parts of the ellipsoidal
passage 4a to 4c, respectively, in the internal space 1 to jet
air in order to improve the fluidity of the powder grains carried
by the gas phase flow and to assure an effective flow of powder
grains along the inside surface of the outer wall 5.
In this crusher, relatively large-sized powder grains (or coarse
powder grains) in the classifying zone 3 are returned to the crushing
zone 2 by the centrifugal force of the gas phase flow carrying powder
grains acting at the outer part of classifying zone 3 that is greater
than the carrying force of the gas phase flow acting at the center
part of the classifying zone 3 whereby relatively small-sized powder
grains (or fine powder grains) are discharged to the exterior through
the fine-powder outlet 30. FIG. 5(c) shows the conditions where
the fine powder grains are discharged to the exterior.
Several examples of test of the jet air flow crusher constructed
as described above will be presented below:
EXAMPLES 1 AND 2
These tests were carried out graphite powder having the 50% average
diameter D.sub.50 =37.6 .mu.m compressed air of 6.0 to 6.2 kg/cm.sup.2
introduced in the compressed-air chamber 7 and the total flow rate
of air being 1.6 to 1.4 Nm.sup.3 /min (or the flow rate of air per
2 mm nozzle was 0.2 to 0.22 Nm.sup.3 /min).
The flow rate of powder to be processed was 2.5 kg/h to 25 kg/h.
All the nozzles 50a to 50f were full opened to jet out the air,
respectively, in Example 1 while the sixth nozzle 50f was closed
in Example 2.
The results of these tests are as shown in FIG. 6 where A indicates
Example 1 while B corresponds to Example 2.
COMPARATIVE EXAMPLE 1
This test was carried out under the same conditions as in Examples
1 and 2 except that the fifth and sixth nozzles 50e and 50f were
closed to form no air flow weir. The result of this test is as shown
by the line C in FIG. 6.
FIG. 6 shows that the formation of the air flow weir improved the
crushing efficiency for powder grains and that the flow rate of
powder to be processed was significantly higher in the embodiment
of the present invention, if the same grain diameter of powder to
be processed was used.
FIGS. 7 and 8 show the other embodiments of the present invention.
The embodiment as shown in FIG. 7 has an almost identical construction
to that shown in FIG. 1 except that two pairs of opposed nozzles
(50e, 50f and 50g, 50h) are provided to form air flow weirs.
The embodiment as shown in FIG. 8 comprises a structural throttle
to limit the flow rate of powder grains carried by the gas phase
flow instead of the air flow weir. In the embodiment as shown in
FIG. 8 a pair of angle blocks 51 and 52 opposing each other is
placed at locations at which the opposed nozzles 50e and 50f were
disposed in FIG. 1 so as to limit the gas phase flow passage 4b
partially and, consequently, to serve as a weir to the powder grains
carried by the gas phase flow.
The form of such a structural weir may be selected experimentally
or experientially, or otherwise based upon the observation of powder
grains flowing through the air flow weir.
As has been described above, the jet air flow crusher according
to the present invention present advantages in that it eliminates
various problems present in the conventional jet air flow crushers,
that it has an excellent processing efficiency and is capable of
providing a sufficient industrial processing capacity, even if relatively
small-sized powder grains are crushed, and that it can provide crushed
powder grains having a size of 10 .mu.m or less on industrial production
scale, while such grains could heretofore be conventionally provided
only by a special crusher having a small processing capacity.
The crusher according to the present invention has a simple construction,
is small and operates very well. |