Abstrict A pair of counterrotating crusher rolls are provided with intermeshing
teeth having configurations especially adapted to accept and positively
feed relatively large portions to be crushed into the nip of the
rolls and to crush the fed material into particles of a relatively
small size.
Claims I claim:
1. In a crusher roll assembly having first and second toothed crusher
rolls, with a nip between them, mounted for and driven in, coordinated
counterrotation about spaced parallel axes to crush material fed
into the nip between the rolls; the number of teeth on said second
roll being less than the number of teeth on said first roll and
said second roll being driven at a higher rate of rotation than
said first roll; the improvement wherein the leading edge of each
tooth on said first roll is a concavely curved surface and the trailing
edge of each tooth on said first roll is a substantially flat surface
substantially radial to the axis of said first roll, generally tangential
lands connecting said leading and trailing edges each tooth on said
second roll having a leading edge surface defined by a substantially
flat surface inclined rearwardly with respect to the direction of
rotation of said second roll and a convexly curved trailing edge
surface generally complementary in shape to the concave leading
edge surface of a tooth on said first roll, the leading and trailing
edge surfaces of each tooth on the second roll being separated by
a generally tangential land, the teeth on the second roll also being
connected by roots which intermesh with said lands on the teeth
of the first roll; the teeth on the first and second rolls being
radially opposite and the axes of rotation of said rolls being spaced
from each other by a distance such that the teeth on the respective
rolls move in overlapping paths through the nip between the rolls
with the teeth on the respective rolls maintained in spaced relationship
to each other, the peripheral spacing of the teeth on the said rolls
being such that counterrotation of said rolls first advances the
substantially flat leading edge surface of a first tooth on the
second roll to a position generally opposite the concave trailing
edge surface of a first tooth on the first roll while disposing
the trailing convex edge surface of a second tooth on the second
roll immediately adjacent the first tooth on the second roll in
the downstream direction in close mating proximity to the leading
concave edge surface of a second tooth on the first roll immediately
adjacent the first tooth on the first roll and downstream thereof,
the land on the said second tooth on the first roll being opposite
a root on the second roll and the substantially flat leading edge
surface of the second tooth on the second roll at this time being
downwardly inclined and generally parallel to the substantially
flat trailing edge surface of a third tooth on the first roll which
is immediately downstream of the said second tooth on the first
roll; the land on the said second tooth on the second roll permitting
the intermeshing second tooth on the first roll and second tooth
on the second roll to radially clear, with continued rotation of
the rolls.
2. The assembly of claim 1 wherein the peripheral spacing of the
teeth is such that counterrotation of said rolls successively advances
the substantially flat leading edges of the teeth of the second
roll into spaced generally parallel relationship with the respective
substantially flat trailing edges of the teeth of the first roll
at a location below a plane containing the axes of rotation of said
rolls.
Description BACKGROUND OF THE INVENTION
The present invention is especially directed to crushing apparatus
in which material to be crushed is fed into the nip between the
teeth of a pair of power driven counterrotating rolls to be crushed
into relatively fine particles.
The present invention is especially directed to an improvement
over the crusher roll assembly disclosed and claimed in a commonly
owned DeVita and Watkins application Ser. No. 296897 filed Aug.
27 1981 and assigned to the assignee of the present application.
As described in the DeVita et al application referred to above,
toothed crusher roll assemblies of the type with which the present
invention is concerned have had practical limitations in crushing
incoming material to particles of the desired fineness in those
situations where the incoming material took the form of relatively
large sized lumps or portions. Crusher roll systems exemplary of
the prior art are those illustrated in patents:
One specific example with which the present invention is concerned
is that of crushing the used sand cores employed in foundry operations,
to recover the sand for use in making additional cores. The comparative
size of the sand cores and the sand particles is such that the prior
art crushing of the cores, or significant portions thereof, had
to be accomplished in a two or three step process in which the material
was passed through successively finer sets of crusher rolls before
the desired particle size could be achieved.
The present invention is especially directed to an improved tooth
form which enables a crusher roll assembly to accept relatively
large sized pieces of material while being operable to crush this
material into relatively fine particles in a single pass through
the roll assembly. Whereas previous machinery has normally accomplished
6:1 reduction, the present invention has exceeded 50:1 with 20
inch size material reduced to under 3/8 of an inch.
SUMMARY OF THE INVENTION
The present invention is especially concerned with a toothed configuration
which provides a positive feeding action on relatively large incoming
pieces of material and at the same time crushes the material into
relatively fine particles while maintaining an adequate clearance
between the teeth on cooperating anvil and crusher rolls.
An anvil roll may be formed with teeth of substantially the same
configuration as that of the anvil roll teeth in the aforementioned
DeVita et al application. The anvil roll teeth are formed with flat
trailing edge surfaces which preferably lie in planes which may
be substantially radial to the axis of rotation of the anvil roll.
The leading edges of the anvil roll teeth are defined by a concavely
curved surface.
The essence of the present invention is found in the shape of the
crusher roll teeth which differs from that disclosed in the above
mentioned DeVita application in two primary respects. First, according
to the present invention, the leading edge surface of the crusher
roll teeth is a substantially flat surface, like that in the DeVita
application, however, in contrast to the teeth of the DeVita et
al application, this generally flat surface is inclined relative
to a true radial plane so that the base of the leading edge of the
tooth is located forwardly, with respect to the direction of rotation,
of the tip portion of the leading edge. The tip of the tooth of
the crusher roll takes the form of a tip portion lying at a constant
radial distance from the crusher roll axis, while the trailing edge
of the crusher roll is convexly curved to a complementary relationship
with the leading edge of the anvil roll teeth.
This configuration allows a closer approach of the substantially
flat leading edge of the crusher roll to the substantially flat
trailing edge of the anvil roll tooth during the crushing operation,
thus achieving a finer particle at the conclusion of the crushing
operation, while still providing adequate clearance between the
teeth of the respective rolls.
Further objects and features of the invention will become apparent
with reference to the following specification and to the drawings.
IN THE DRAWINGS
FIG. 1 is a side elevational view, partially in cross section,
of a crusher roll assembly embodying the present invention;
FIG. 2 is a detail side elevational view showing the intermeshing
teeth of the anvil and crusher rolls of the apparatus of FIG. 1;
FIG. 3 is a top plan view of the anvil roll;
FIG. 4 is a top plan view of the crusher roll; and
FIGS. 5 6 7 and 8 are sequential views showing the relationship
between the teeth on the respective rolls as they pass through the
nip.
Referring first to FIG. 1 an apparatus embodying the present invention
includes a frame or housing designated generally 10 within which
an anvil roll 12 and a crusher roll 14 are mounted for counterrotation
about spaced parallel horizontal axes in the directions of rotation
indicated by arrows a and b. A drive motor 16 mounted upon frame
10 is operable to drive rolls 12 and 14 in counterrotation at predetermined
speeds of rotation as by means of a chain and sprocket drive designated
generally 18. As indicated, rolls 12 and 14 are driven in opposite
directions of rotation so that the teeth on the exterior of the
respective rolls move downwardly through the nip 20 of the rolls.
Material to be crushed by the counterrotating rolls 12 and 14 is
fed into the nip via a hopper 22 is carried downwardly by the teeth
on rolls 12 and 14 through nip 20 and the material is crushed during
its passage through the nip.
Referring now particularly to FIGS. 2 and 5-8 it is seen that
the teeth 24 on anvil roll 12 are formed with a concavely curved
leading edge 26 and a flat trailing edge 28 the trailing edges
28 of the teeth of anvil roll 12 lying in planes which extend substantially
radially with respect to the axis of rotation of roll 12. An peripheral
tip portion 30 which lies at a constant radial distance from the
axis of roll 12 extends between the radially outer ends of teeth
edges 26 28.In FIGS. 5-8 first, second, and third teeth 24 in
a clockwise direction, are designated 24 C, 24B, and 24A respectively.
The concave surface forming the leading edge of tooth 24C is designated
28C, and the concave surface forming the leading edge of tooth 24B
is designated 28B.
The teeth 32 of crusher roll 14 includes a substantially flat surface
34 which is inclined rearwardly from a true radial plane with respect
to the direction of rotation of crusher roll 14. The trailing edge
surfaces 36 of teeth 32 of crusher roll 14 are convexly curved and
have a radius of curvature just slightly less than the radius of
curvature of the concave leading edges 26 of the anvil roll teeth.
A relatively short, peripheral tip portion 38 lying at a constant
radial distance from the axis of roll 14 extends between the radially
outer ends of the leading and trailing edges 34 36 of the crusher
roll teeth, and the crusher roll teeth are spaced circumferentially
from each other by bottom lands or roots 40. In FIGS. 5-8 first
and second teeth 32 in a counterclockwise direction, are designated
32B and 32A respectively. The convex surface forming the trailing
edge of tooth 32A is designated 36A and the flat surfaces forming
the leading edges of teeth 32B and 32A are respectively designated
34B and 34A.
It will be noted that, in the embodiment illustrated, anvil roll
12 is shown as having ten teeth, while crusher roll 14 has seven
teeth. The respective rolls are driven by drive motor 16 and the
chain and sprocket drive 18 at different speeds whose ratio is
the inverse of that of the ratio of the number of teeth on the respective
rolls so that the intermeshing relationship of the teeth, as shown
in FIGS. 5-8 remains constant, with a given tooth on crusher roll
14 moving into intermeshed relationship with a different tooth on
anvil roll 14 during successive revolutions of the two rolls.
The crushing action achieved by the toothed configuration described
above is best seen in the sequential views of FIGS. 5-8 inclusive.
Referring first to FIG. 5 tooth 32A of crusher roll 14 is shown
in a position of maximum intermeshed relationship between teeth
24A and 24B of anvil roll 12. Tooth 32B of crusher roll 14 is moving
toward intermeshed relationship between teeth 24B and 24C of anvil
roll 12 but at the particular stage shown in FIG. 5 is still substantially
spaced from any adjacent surface of anvil roll 12 so that a piece
of material to be crushed (indicated in broken lines at P) can fall
from hopper 22 (FIG. 1) to the position illustrated in FIG. 5.
Comparing FIG. 6 with FIG. 5 in FIG. 6 tooth 32B of crusher roll
14 has moved toward the space between teeth 24B and 24C of anvil
roll 12 and the spacing between the tip 38B and tooth edge 28C has
been substantially reduced from that of FIG. 5. This reduction in
spacing might very well crush the particle P indicated in FIG. 5
into at least two segments, which are, in FIG, 6 trapped between
the advancing leading edge of tooth 32B of crusher roll 14 and the
pocket now defined between edges 26B and 28C of anvil roll 12.
Referring now to FIG. 7 it is seen that the tip portion 38B of
crusher roll tooth 32B has advanced from the FIG. 6 position to
a new position in which it is beginning to underlie the concavely
curved edge 28C on anvil roll 13 the leading edge 34B of tooth
32B on crusher roll 14 now defining, with edges 26B and 28C of anvil
roll 12 a substantially closed, generally triangular chamber in
which material to be crushed is now trapped.
Further rotation of the rolls from the FIG. 7 position to that
of FIG. 8 shows this last mentioned triangular chamber defined by
edges 34B on the crusher roll and edges 26B, 28C of the anvil roll
to now be of substantially reduced volume, further rotation of the
rolls from the FIG. 8 position shifting teeth 32B and 24B to the
position occupied by teeth 24A and 32A in FIG. 5.
It will be noted that the provision of tip portions 38B on the
teeth of crusher roll 14 provides clearance between the teeth on
the respective rolls, as best appreciated from FIGS. 7 and 8. It
will be noted that the primary crushing surfaces defined by the
leading edges 34 of the crusher roll teeth and the flat trailing
edges 26A of the anvil roll teeth move into substantial parallelism
with each other at a point below the plane containing the axes of
rotation of the two rolls, the final relative movement of these
teeth being a sort of rolling action of the leading edges of the
crusher roll teeth generally radially outwardly along the substantially
flat surface of the trailing edges of the anvil roll teeth.
Because the volume of material trapped between the teeth of the
respective rolls, as at the point illustrated in FIG. 7 may have
a volume too large to be fully reduced during the crushing operation
to the available clearance volume between the respective teeth,
the teeth 32 on crusher roll 14 are arranged in axially aligned
rows in axially spaced relationship to each other, as best seen
in FIG. 4. The spaces between the teeth indicated at 42 in FIG.
4 are so located that the teeth in adjacent rows are axially staggered
relative to each other so that the teeth in one axially extending
row are aligned with the spaces 42 between the teeth of the next
adjacent row. The teeth 24 on anvil roll 12 on the other hand,
extend continuously for the entire axially length of the roll as
shown in FIG. 3.
While one embodiment of the invention has been described in detail,
it will be apparent to those skilled in the art that the disclosed
embodiment may be modified. Therefore, the foregoing description
is to be considered exemplary rather than limiting, and the true
scope of the invention is that defined in the following claims.
|