Abstrict A pair of counter-rotating crusher rolls are provided with intermeshing
teeth having configurations especially adapted to accept and positively
feed relatively large lumps or portions to be crushed into the nip
of the rolls and to crush the fed material into particles of a relatively
small size.
Claims We claim:
1. In a crusher roll assembly having radially intermeshing, 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 means for driving said second roll 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, said leading and trailing tooth edges on
the first roll being connected by lands; each tooth on said second
roll having a leading edge surface defined by a substantially flat
surface and a convexly curved trailing edge surface generally complementary
in shape to the leading edge surface of a tooth on said first roll;
the teeth on the second roll being connected by roots which intermesh
with said lands on 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 tooth spacing on said respective
rolls being such that counterrotation of said rolls advances the
substantially flat leading edge surface of a first tooth on the
second roll toward 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 which is immediately
downstream from said first tooth on the second roll generally opposite
the leading concave edge surface of a second tooth on the first
roll which is immediately downstream of said first tooth on the
first roll, the substantially flat leading edge surface of the second
tooth on the second roll at this time being generally opposite and
generally parallel to the substantially flat trailing edge of still
a third tooth on the first roll which is immediately downstream
of said second tooth on the first roll.
2. The invention defined in claim 1 wherein the teeth on said first
roll extend continuously substantially the entire axial extent of
said first roll, the teeth on said second roll being disposed in
intermittant spaced relationship to each other in axially aligned
rows.
3. The invention defined in either of claims 1 or 2 wherein the
flat leading edges of the teeth on said second roll lie in respective
general planes extending substantially radially of the axis of said
second roll.
4. The invention defined in claim 2 wherein the teeth in one of
said axially aligned rows are axially offset from the teeth in an
adjacent axially aligned row.
5. The invention defined in claim 1 wherein drive means coupled
to both of said rolls drives the respective rolls at respective
speeds inversely proportional to the number of teeth on the roll.
6. The assembly of claim 1 in which the generally parallel condition
of said flat leading and flat trailing edge surfaces occurs substantially
in a plane connecting the axes of rotation of the 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, counter-rotating rolls driven at
different speeds to be crushed into relatively fine particles. In
the usual case, the rolls are provided with somewhat intermeshing
teeth which must act to drive incoming lumps into the nip. The teeth
are so designed that the teeth on one roll do not contact the teeth
on the other, but, as the teeth pass through the nip between the
rolls, they approach their minimum spacing from each other, and
it is this minimum spacing which defines the maximum size of particles
which are crushed by their passage through the nip. U.S. Pat. Nos.
which disclose such crushers are: 48244 842681 1435330 1750941
1824088 2578540 2588900 3208677 3240436 3474973.
A typical operation employing crusher roll pairs of the type referred
to above is found in foundries where used sand cores employed in
the casting operations are crushed in order to salvage the sand
for use in making up new cores.
Most presently available crusher rolls employed in operations of
the type described above are found wanting from the standpoint of
the range of reduction in size which they can achieve. Those roll
pairs which will accept and positively feed relatively large lumps
into the crushing nip will discharge relatively large sized crushed
particles which are too large for their intended use, while those
roll pairs which will crush particles to the desired degree of fineness
will not adequately feed relatively large lumps. In the previously
mentioned example of crushing foundry sand cores, the cores or parts
thereof recovered are frequently of relatively large over-all dimension
as compared to the size of the sand particle desired, and most core
crushing operations require passage of the material through two
or three or more successively finer pairs of crushing rolls before
particles of the desired degree of fineness are obtained.
It is the purpose of the present invention to provide a tooth configuration
for crushing rolls of the type described above which will accept
material of relatively large over-all dimension and crush the material
into relatively small particles so that objects, such as foundry
sand cores, can be reduced to particles of the desired fineness
in a single crushing operation. Whereas previous machinery has normally
accomplished 6:1 reduction, the present construction is designed
to greatly exceed this.
SUMMARY OF THE INVENTION
In accordance with the present invention, a first or anvil roll
is constructed with teeth having flat trailing edges lying in respective
radial planes substantially intersecting the axis of rotation of
the roll. The leading edge of the teeth on the anvil roll are concavely
curved.
A mating crusher roll is provided with teeth of a shape complementary
to those of the anvil roll--that is the crusher roll teeth have
a flat leading edge lying in a plane radial to the axis of the crusher
roll and are formed with a convexly curved trailing edge generally
complementary to that of the concavely curved leading edges of the
anvil roll teeth.
The axes of rotation of the two rolls are so spaced that the paths
of the teeth of the respective rolls overlap, but the teeth on the
respective counter-rotating rolls do not come in contact with each
other. The toothed configuration described provides, just above
the nip between the rolls, a relatively wide upwardly opening pocket,
while the flat edges on the teeth of the respective rolls move into
a closely spaced parallel relationship with each other as the teeth
pass downwardly through the horizontal plane containing the axes
of rotation of the two rolls.
Further objects and features of the invention will become apparent
by reference to the drawings and to the following specification.
IN THE DRAWINGS
FIG. 1 is a schematic 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 rotation
about spaced parallel horizontal axes. A drive motor 16 mounted
upon frame 10 is operable to drive rolls 12 and 14 in counter-rotation
at predetermined different 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 direction of rotation so
that the teeth on the exterior of the respective rolls move downwardly
through the nip 20 between the rolls. Material to be crushed by
the counter-rotating 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
the nip 20 the material being fully crushed during its passage
through the nip.
The present improvement is directed to the configuration of the
teeth on the rolls 12 and 14. This configuration, as will be developed
below, is especially well adapted to receive relatively large sized
lumps of material from hopper 22 to positively feed these relatively
large lumps downwardly into the nip 20 and to crush them into relatively
small sized particles. The configuration of the teeth on rolls 12
and 14 is best seen in FIGS. 2 and 5-8.
Referring to FIG. 2 it is seen that the teeth 24 on anvil roll
12 are formed with a flat trailing edge 26 (the designation "trailing"
being with respect to the direction of rotation of roll 12 indicated
by arrow a). The flat surface of trailing edge 26 lies in a general
plane which is substantially radial to the axis of anvil roll 12.
The leading edge 28 of tooth 24 is concavely curved and is preferably
of a substantially constant radius of curvature. A peripheral tip
surface 30 lying at a constant radius from the axis of roll 12 extends
between the leading and trailing edges of each tooth 24 24', etc.
of anvil roll 12.
The teeth 32 of crusher roll 14 which is driven in the direction
identified by arrow b are generally complementary in shape to the
teeth of anvil roll 12. The leading edge 34 of each crusher roll
tooth 32 is flat and lies in a general plane substantially radial
to the axis of crusher roll 14 while the trailing edge 36 of crusher
roll tooth 32 is convexly curved at substantially a constant radius
of curvature which is slightly less than the radius of curvature
of the concavely curved leading surfaces 28 of anvil roll teeth
24.
From FIG. 2 it will be noted that although the diameter of the
rolls 12 and 14 is the same, the number of teeth on each roll differs.
In the embodiment shown in the drawings, anvil roll 12 has twelve
teeth 24 while crusher roll 14 has eight teeth. The respective
rolls are synchronously driven at different speeds of rotation so
that the same intermeshing relationship between the teeth is maintained--that
is the product of the number of teeth upon a roll and its rate of
rotation is the same for both rolls. This arrangement assures that
a given tooth on one roll is matched with different teeth on the
other roll during successive revolutions and promotes even wearing
of the teeth.
FIGS. 5 6 7 and 8 show successive steps in the rotation of the
rolls 12 and 14 to illustrate the crushing action exerted by the
teeth.
Referring first to FIG. 5 in this view, tooth 24A on anvil roll
12 has its trailing surface 26A disposed in spaced opposed parallel
relationship to the leading edge 34A of tooth 32A on crusher roll
14. The spacing indicated between edges 26A and 34A in FIG. 5 represents
essentially the maximum particle dimension of material crushed between
the two rolls, the crushing action exerted upon material caught
between the teeth of the two rolls being performed substantially
entirely by the movement of the flat leading edge 34A of the tooth
32A toward the flat trailing edge 26A of the opposed tooth.
At the same time, it will be noted that there is a substantial
spacing between the leading edge 34B of the next trailing tooth
32B on crusher roll 14 and the pocket on the anvil roll 12 defined
by the trailing edge 26B of the next trailing tooth 24B on anvil
roll 12 and the leading edge 28C of the next trailing tooth 24C.
This particular space is relatively large, and lumps to be crushed
which are fed from hopper 22 (FIG. 1) and can be received within
this space will be subjected to a crushing action as the respective
rolls 12 and 14 are counter-rotated from the FIG. 5 position.
Referring now to FIG. 6 both rolls have been advanced slightly
from the position shown in FIG. 5 the flat tooth surfaces 26A and
34A having now passed below the horizontal so that the tip of tooth
32A has started to scrape crushed particles outwardly off the surface
26A of tooth 24A. In FIG. 6 the leading edge 34B of tooth 32B has
moved further toward the horizontal from the FIG. 5 position, and
any large pieces of material captured underneath this surface are
now being pressed toward the pocket defined by surfaces 26B and
28C on anvil roll 12.
Referring now to FIG. 7 tooth 32A has now substantially cleared
tooth 24A, while tooth 32B is now moving into a relationship with
anvil roll 12 such that surface 34B of tooth 32B is substantially
closing the space at which material enters the nip between the two
rolls to trap incoming objects or lumps underneath surface 34B.
Further rotation of the two rolls brings the teeth 24B and 32B into
the relationship shown in FiG. 8 in which a substantially closed
chamber is now created between teeth 32B and 24B. Further rotation
of the respective rolls brings the surfaces 34B and 26B into the
same relationship as the corresponding surfaces 34A and 26A illustrated
in FIG. 5 this last transition crushing the material trapped under
surface 34B which, because of the greater speed of rotation of crusher
roll 14 as compared to that of anvil roll 12 simply reduces the
volume of the "chamber" between the opposed flat surfaces
as they move from their relationship shown in FIG. 8 to that shown
in FIG. 5.
One form of tooth arrangement is shown in FIGS. 3 and 4. As illustrated
in these two figures, the teeth 24 on anvil roll 12 are continuous
over the entire axial length of the roll, while the teeth 32 on
crusher roll 14 are disposed in axially aligned rows with spaces
38 between adjacent teeth within each axial roll. The teeth in adjacent
rolls are staggered with respect to each other so that a space 38
between two adjacent teeth in one axial row is aligned with a tooth
32 in the next adjacent row. This arrangement of teeth permits excess
material which may have been trapped within the "chamber"
as shown between surfaces 34B and 26B in FIG. 8 to be expressed
axially of tooth 32B into the spaces 38 at opposite sides of the
tooth as this "chamber" is reduced in volume during the
crushing operation. Without this relief, it is possible that an
excess of quantity of material might be trapped between the teeth
to jam or stall the drive.
While one embodiment of the invention is described in detail above,
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. |