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Патент USA US2112359

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March 29, A193s.
2,112,359
J. CRITES
ROTARY BowL. MILL
Filed June 2_9, 1956
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March 29, 1938.
J. CRITES
> 2,112,359
ROTARY ßowrJ MILL `
Filed June 29, 1936
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Patented Mar. 29, 1938
UNITED ÍSTATES PATENT OFFICE
2,112,359
ROTARY BOWL MILL
Joe Crites, Evanston, lll., assignor, by mesne as
signments, to Combustion Engineering Com
pany, Inc., a corporation of Delaware
Application June 29, 1936, Serial No. 87,928
6 Claims.
This invention relates to certain new and use
ful improvements in a rotary bowl mill adapted
to grind and pulverize solid materials, such as
coal, rock, etc.
Brieily described, the mill is of the type in
cluding an upwardly opening bowl or container
which is rotatable about a central vertical axis
within a substantially closed housing or casing.
One or more grinding rollers, each freelyv rotat
10 able about its own axis, are suspended within the
bowl so as to be forced under pressure toward the
upwardly and outwardly projecting inner side
wall of the bowl, or the material carried thereby,
the rollers being rotated by contact with this
15 material. The side walls of the bowl are spaced
from the side walls of the container so as to pro
vide an annular air passage around the bowl, air
being admitted to the lower portion of the cas
ing and drawn or forced under pressure through
the annular passage with a whirling motion, and
thence over the bowl and through outlets in the
vided on the wall of the casing at the outer side
of the air passagefthese ribs being inclined up
wardly .in the direction of rotation of the air
stream. The whirling materials are held closely
against the casing wall and are guided by these 5
ribs upwardly toward the deflectors by' which
they are thrown back into the bowl.
The principal object of this invention is to pro
vide an improved bowl mill of the type brieiiy
described hereinabove and disclosed more in de- 10
tail in the specifications which follow.
Another object is tn_provi'de improved means
for returning into the bowl for further treatment
such grindable materials as iind their way into
15
the annular air passage surrounding the bowl.
Another object is to provide improvedvspiral
directing ribs in the mill casing for directing ma.
terials upwardly through the air passage.
`
Another object is to provide spiral deilecting
ribs in combination with stationary deflectors for 20
returning material into the grinding bowl.
Other objects and advantages of this invention
upper wall of the casing to a separator. Sum- «
will be more apparent from the following detailed
ciently pulverizedA material is carried in suspen
sion in the air stream from the casing into and .description of one approved form of mill con
structed and operating according to the princi- 25
through the separator. The material to be pul
of this invention.
verized is introduced from above into the central ples
In the accompanying drawings:
portion of the bowl, and insuiilciently pulverized
through
material is also returned from the separator into
the central portion of the bowl Stationary de-l
flectors are positioned in the casing at the outer
side of and above the annular air passage to re
40
Fig. 1 is a central vertical section
the improved mill assembly.
Fig. 2 is a partial plan view and partial hori- 30
zontal section. The upper left-hand portion of
turn insuiiiciently pulverized material thrown
this figure is taken substantially on the line 2--2
from the bowl back into the bowl for further
treatment. "I‘he heaviest waste materials fall
through the annular passage into the lower por
tion of the casing or housing, and Scrapers car
ried by the rotating bowls` direct this material
toward a discharge opening in the bottom of the
casing. A mill of the general type described here
substantially .on the line 2’--2' of Fig. 1.
Fig. 3 is a perspective view oi.' the inner por-- 35
tion of one side of the mill casing, showing the
stationary spiral ribs ‘and deflecting vanes.
This assembly comprises the casing or housing
inabove is disclosed and claimed inapplicant’s
former application Serial No. 25,789, ñled June
10, 1935.
In -a mill of this type, it has been found that
some of the heavier material particles thrown
from the rotating bowl and not suihciently pul
of Fig. 1, whereas the right-hand portion is taken
A, the rotatable bowl or container B which is ,
driven and supported by the mechanism indi- 40
cated generally at C, the grinding rollers D, and
the mechanisms indicated generally at E for`
supporting and exerting adjusted pressure on the
rollers.
The means shown at F feeds material _
to be ground into the mill, and the conduit sys-> 45
tem indicated generally at G delivers air under
pressure into the lower portion oi' the mill hous
verized do not reach the stationary deiiectors, or
are not returned to the bowl thereby, and these
ing. At_ H is indicated generally the mechanisms
heavier material particles find their way down
discharging waste materials from the mill.
wardly into the whirling air stream in the annu ,for
lar passage between the casing and the upwardly while at K is shown the separator through which 50
the suñiciently pulverized material is carried out
and outwardly extending side wall of the rotat
in
suspension and from which insuiiiciently pul
ing bowl. The purpose of the present improve
ments is to provide means for returning this ma-- verized material is delivered back into the bowl B.
terial to the bowl for further grinding treatment. At L is indicated generally the devices which
more particularly form the subject matter of this 55
More speciñcally, spiral ribs or vanes are pro
2,112,359
er D, and the apexes of the conical grinding sur
material thrown from the bowl back into the bowl faces of the rollers D and the grinding ring I8, all
meet in a common point positioned below the .
for further grinding treatment.
'I'he enclosing casing or housing A comprises bowl so that there will be a true rolling engage
the base plate I which rests upon the concrete ment between the surfaces of the rollers and
pedestals or foundation 2, the annular side wall grinding ring.
The shaft 26 projects up through an opening 21
3, and the closure or cover plate 4. _The base
plate I comprises a central bearing portion 5 in in cover plate I2 and the tapered upper end por
which the hub 6 of bowl B is journaled. The tion 28 of shaft 26 is secured in the hub 29 of
the lever mechanism indicated generally at E by
10 annular side wall 3 comprises a lower substan
tially cylindrical portion 1, a central upwardly means of which the roller assembly is supported
diverging portion 8, and an upper, somewhat and adjusted. This lever comprises a split hub
larger cylindrical portion 9 to the upper edge 30 which is locked on the central portion of a
of which the cover plate 4 is secured. This side short horizontal shaft 3I which is journaled at
its ends in brackets 32 projecting upwardly from
15 wall may be provided with a suitable liner indi
the cover plate I2. A compression spring 33 is
cated generally at I0. The cover plate 4 is pro
vided witha plurality of openings I I each closed confined between the outwardly projecting end
by an individual cover plate I2. Each opening portion 34 of the lever E, and a plate 35 adjustably
supported by bolts 35' from the cover plate I 2.
II permits the insertion or removal of one of
the roller assemblies D, and the roller supporting This spring tends to swing the lever mechanism
and adjusting mechanism E is carried by the E in a clockwise direction, as seen in Fig. 1, so as
cover plate I2. The main cover plate 4 is also to force the roller D toward the grinding ring I8.
provided with a plurality of outlet openings I3 Preferably an adjustable limiting plate 36 carried
which communicate with passages leading up by the upper ends of the bolts 35’ serves to limit
the movement of the roller in this direction so 25
25 into the separator K. A central opening I4 in
that a slight clearance will remain at all times
cover plate 4 communicates with the lower dis
between the surface of the grinding roller and
charge end of the separator K, as will be here
inafter described. Except for the openings re vthe grinding ring I8. It will be apparent that
ferred to above, the top of the casing may be spring 33 tends to swing the lever E about its
invention, for returning insufficiently pulverized
pivot so as to move the roller D toward the grind
30 considered as entirely closed.
'I'he bowl or container B comprises a central
shallow table portion I5 formed by a. disk-like
bottom wall which slopes upwardly and outwardly
at a small angle to the horizontal from the
35 central axis of rotation, and an annular grinding
wall formed by an upwardly projecting outer
ñange portion I6 which ñares outwardly at a
small angle to the vertical. Preferably the-in
clination of the outer bowl wall I6 is substan
40 tially the- same as that of the adjacent casing
wall 8 so as to leave an annular air passage I1
therebetween, as hereinafter described. Pref
erably a separate grinding track or ring I8 is
mounted on the inner surface of the inclined
45 side Wall I6 of the bowl.
The driving assembly C comprises a central
vertical drive shaft I9 which is keyed Within the
hub 6 of the- bowl B. The upper and lower mem
bers 28 and 2i of a gear casing are secured to
50 gether and to the base plate I so as to enclose
and lubricate‘the gears for rotating shaft I9.
A worm wheel 22 keyed on shaft I9 meshes with
and is driven by a worm 23 suitably journaled in
the gear casing and connected with a driving
-55 motor or other suitable driving means not here
shown.
f
_ ‘There may be one or more of the grinding roll- -.
ers D, depending on the size of the mill, there
being three of these rollers in the example here
60 shown.
These rollers will be equally ' spaced
about the central axis so as to distribute the
thrust on the grinding bowl B. Each roller com
prises a removable and renewable grinding tread
24 carried by the sleeve assembly 25 which is
65 freely rotatable on the non-rotary supporting
shaft 26.
This type of grinding roller is well
known in the art and need not be here described
in detail. The roller 24 is rotatable by contact
30
ing ring I 8. As material to be ground finds its
way between roller D and grinding ring I 8, the
spring 33 will yield to permit the roller to swing
inwardly, but will exert a predetermined outward
pressure on this material, the pressure being de
termined by proper adjustment of the spring
mechanism.
In case there is no material on the
grinding ring I8, the small clearance provided
will prevent hammering of the rollers cn the
grinding ring and thus reduce noise and wear on 40
the grinding surfaces.
It will be understood that the above descrip
tion is- of one of the roller units D and E, each
of these units consisting of an assembly such as
just described hereinabove. By removing the in- l
dividual cover plate I2, each of these grinding
units can be removed and the roller lifted out of
the housing through opening il.
'I'he material to be ground and pulverized is fed
into the housing by the feed mechanism F, which
in the example here shown comprises a hopper
3'I, a rotary feeder 38, a horizontal screw con
veyor 39, and a chute 40 which extends down
into the bowl B through one of the openings I3
in the top wall 4 of the housing.
Air from any suitable source is delivered
through pipe or conduit 4I into the pipe exten
sion 42 of casing wall 3. This air passage ex
tends tangentially into the lower portion of the
mill housing through inlet opening 43 so as to
create a whirling movement of the air within
the housing. This air is delivered into the hous
ing under pressure, but this pressure may be
created by a suction at the outlet of separator
K. 'I'his air stream, the whirling movement of 65
which will be increased by the rotation of bowl
B which rotates in a clockwise direction as viewed
from above, passes upwardly through the an
nular channel I1 between the rotating bowl and
70 with the grinding ring I8, or more -properly by the side wall 8 of the casing, thence inwardly
contact with the material to be ground which is over the bowl and out through the openings I3 in
interposed between the tread 24 of the roller and the cover plate into the separator K.
the grinding ring I8 as will be hereinafter ap- The material in bowl B will move by centrifu
parent. Preferably the vertical axis of the bowl, gal force toward the outer walls I6 of the bowl
and will be ground and pulverized between the
75 the central axis of rotation of each grinding roll
3
2,112,359
rollers D’and the grinding ring I8. Due to the
small outward inclination of the outer walls I6 of
the bowl, centrifugal force will hold a compact
bed of the material against> the grinding ring I8,
through which bed of material -the rollers D
grind, and this material will move slowly up
wardly before being thrown or discharged from
the upper edge of the bowl. A plurality of sta
tionary deilectors 44 are positioned at spaced
intervals circumferentially of the housing in the
upper and outer portion thereof adjacent the
side wall 9 and top wall 4. These deflectors are
at the outer side of and above the annular air
passage I1, and are in the form of substantially
vertical vanesvwhich extend diagonallyinward
from the outer wall 9 in the direction of rota
tion of the bowl. A movable annular deflector
indicated generally at 45 is mounted on the upper
edge portion of the side wall I6 of the bowl.
This deflector may be provided with an inner
surface sloping upwardly and outwardly toward
the stationary deñectors 44, or may be in the
form of an annular angleplate such as here
shown. Material from the bowl will till in this
angle so as to provide an» upwardly and out
wardly sloping surface, and material which would
otherwise be thrown substantially horizontally
by centrifugal force will be directed upwardly
and outwardly by this sloping surface toward the
30 stationary deilector vanes 44. Due to the rather
lrapid rotation of bowl B this discharged material>
will be thrown forwardly or tangentially sub
stantially in the direction of rotation of the bowl,
and at the same time will be directed upwardly
so as to contact with the stationary deilectors
44. 'I'his material is also projected through the
air stream which is moving spirally upward
through the annular passageÍ I1', this air stream
assisting the centrifugal _force `-imparted by the
4.0 bowl to carry the material îforwardly andup
wardly into forcible engagement with the sta
tionary deilectors 44. The air stream is of suñl
cient volume and velocity to carry sumciently
pulverized materialin suspension, and such ma
terial will be maintained in suspension by the
air stream andïeventually carried out through
the upper outlet openings I3. Larger particles of
material which have not been suñiciently pul
verized o_r reduced in size and -which are too
50 heavy to be carried out in suspension in the air
stream will be thrown back through the air
stream by the deflecting vanes 44 into the central
portion of the bowl B and thus returned
through the grinding cycle. The heavier and
55 larger particles of waste material which cannot
be ground in the mill and are to be rejected
through passage I1 and thence returned into the
mill.
The mill as hereinabove described is substan
tially of the general type disclosed and claimed
in the copending application of Crites, Serial No.
25,789, hereinabove referred to. In the opera
tion of this mill it has been found that some
insuniciently pulverized material which is suit
able for further grinding, and which it is not
desired to discharge through chute 48 as waste
material, finds its way into the air passage I1 be
tween the rotating bowl B and the casing A.
These material particles may be too heavy to
reach the deflectors 44 and rebound into the
mill, or may be thrown out in such a direction 15
as to miss the deñectors 44, or for some other
reason these heavier material particles find their4
way into the air passage I1. These material par
ticles will be caused to rotate or whirl in this pas
sage I1 closely adjacent the casing wall 8, or 20
the liner Ii! therein. According to the present
improvements, the liner sections I0’ within the
portion 8 of the easing wall are formed with up
wardly inclined ribs 5I, which may be in the
form of portions of spirals extending in the gen 254
eral direction of the whirling air currents. These
ribs `need only extend partially across the air
passage, since all of the whirling materials will'
follow quite closely against the> inner surface
of the liner plates I0'. The whirling materials 30
will engage with the upper surface of the ribs 5I
and be directed upwardly so as to eventually con
tact the stationary deflectors 44 and be thrown
back into the bowl. As a result of this improve
ment there is less waste through the discharge
chute 48 anda greater percentage of the mate
rial is eventually pulverized to the desired extent
and carried out in' the air stream into separa
tor K.
The separator K may take a variety of forms,
lt being here shown as of the general type dis
closed and claimed in the copending application
of Crites, Serial No. 62,450, filed February 5, 1936.
The passages 52 extend upwardly from the out
let opening I3 and then expand upwardly, out
wardly and circumferentially to merge into the
annular chamber 53 at the upper end of the sep
arator. This annular chamber 53 communicates
through a series of openings 54 in its inner wall
with the central expansion chamber 55. The
vanes or deñectors 56 at the sides of openings 54
impart a whirling movement to the air entering _
expansion chamber 55.
This air stream, car
rying-the >suiliciently pulverized material in sus
are thrown outwardly from the bowl in a more
pension, will be drawn out through the central
conduit 51 which projects down at its lower end
into expansion chamber 55 and which con
force as the bowl is rotated. IIi'hese scrapers car
out in such an air stream.
at its upper end with a suitable pipe or con
horizontal direction and fall back through pas ‘ nects
sage I1 into the lower chamber 46 beneath the duit 58 leading to a separator or other place of (Si)
discharge Where the pulverized material is with
60 bowl.
drawn from the air stream. lnsufliciently pul
The discharge mechanism H comprises a dis
verized material drops out of the air stream in
chargel opening 41 extending down from cham
the expansion chamber 55 and is directed by the
ber 46 through the base plate I and communi
conical lower portion 59 downwardly `and through
eating with the discharge chute 48. A down
wardly opening one-way valve 49 permits this central chute I4 into the grinding bowl B. l Since» ‘
waste material to flow out through chute 48 there is a tendency for air to be drawn upwardly
while minimizing the inflow of air through this from the mill housing through opening I4 and di
chute. A plurality of Scrapers 50 are pivotally rectly out through the upper central outlet 51,
mounted at their inner ends on the lower portion means is preferably provided to prevent insuf
of bowl B so as to swing outwardly by centrifugal ficiently pulverized material from being carried
ry material deposited in chamber 46 around into
In some installations,
some type of one-way valve is provided in the
position,` to be discharged through opening 41.
discharge outlet I4.
Lighter‘material `stirred up by these scrapers
will be carried up by the whirling air stream
As here shown a hollow con
is supported within the lower central portion 75
ical deñector 60 with its larger end at the bottom
4
of the separator.
2,112,359
A plurality of spiral vanes 6I
are mounted on the inner walls of cone 59 below
the deñector 60. The deiiector 60 serves a two
fold function. In the iirst place its tapered up
per surface tends to puncture the vortex formed
by the whirling air stream and thus prevents
materials being sucked up through the center of
the vortex and out through the upper outlet
opening. In the second place, air tending to
10 flow up through the center of the bottom dis
charge opening I4 will be caught by the lower
end portion of this cone and forced to flow out
wardly toward the side walls of cone 59. This
air will be caused to join in the whirling motion
of the larger air stream within this cone 59, and
any materials that have been picked up by this
upwardly flowing air current will be thrown out
wardly against the walls of the cone and caught
beneath the vanes 6I and thus carried down
As a re
sult substantially none of the heavier material or
20 wardly toward the discharge outlet I4.
tween the outwardly and upwardly extending
outer wall of the bowl and the enclosing wall of
the casing, an inlet opening in the lower por
tion of the casing through which air is delivered
under pressure, an outlet opening for the air
stream in the upper portion of the casing, non
rotary deiiecting vanes positioned inv the casing
upwardly and outwardly from the periphery of
.the bowl at the outer side of the air passage for
deñecting material thrown thereagainst from the 10
bowl back through the air stream into the bowl,
and ribs carried by the casing at the outer side
of the air passage and inclined upwardly in the
direction of rotation of the bowl for directing ma
terial in said passage toward the deflecting vanes. 15
4. A mill comprising a closed casing, a bowl
mounted within the casing for rotation about a
central vertical axis, means for rotating the bowl,
means for introducing material to be ground
into the central portion of the bowl, freely ro 20
tailings can be carried upwardly through th'e cen
tatable grinding rollers suspended within the
bowl in position to be rotated by contact with
tral portion of the separator or classifier even
the material carried on the inner surface of the
though this bottom discharge outlet I4 is open at
25 Aall times.
I claim:
1. A mill comprising a closed casing, a bowl
mounted within the casing for rotation about a
central vertical axis, means for rotating the bowl,
30 means for introducing into the bowl material to
be ground, means within the bowl for grinding
the material, there being an annular air passage
between the outwardly and upwardly extending
outer wall of the bowl and the enclosing wall of
35 the casing, means for forcing air under pressure
upwardly through the passage with a whirling
motion in the direction of rotation of, the bowl,
non-rotary defiecting vanes positioned in the cas
ing at the outer side of and above the passage for
40 directing material thrown from the bowl back
through the air stream into the bowl, and ribs
carried by the casing wall at the outer side of the
air passage and inclined upwardly in the direc
tion of movement of the whirling air stream for
45 directing material in the passage toward the de
fiecting vanes.
2. A mill comprising a closed casing, a bowl
mounted within the casing for rotation about a
central vertical axis, means for rotating
50 the bowl, means for introducing -into the bowl
material to be ground, means within the bowl for
grinding the material, there being ‘an annular
air passage between the outwardly and upwardly
extending outer wall of the bowl and the enclos
55 ing wall of the casing, means for forcing air un
der pressure upwardly through the passage with
a whirling motion in the direction of rotation of
the bowl, non-rotary deilecting vanes positioned
in the casing at the outer side of and above the
60 passage for directing materialtthrown from the
bowl back through Ythe air stream into the bowl,
and spiral ribs carried by the casing wall at the
outer side of the air passage and inclined up
wardly in the direction of movement of the whirl
65 ing air stream for directing material in the pas
sage toward the defiecting vanes.
3. A mill comprising a closed casing, a bowl
mounted within the casing for rotation about a
central vertical axis, means for rotating the bowl,
means for introducing material to bev ground into
the central portion of the bowl, freely rotatable
grinding 'rollers suspended within the bowl in po
sition to be rotated by contact with the material
carried on the inner surface of the outer wall of
75 the bowl, there being an annular passage be
outer wall of the bowl, there being an annular
passage between the outwardly and upwardly 25
extending outer wall of the bowl and the en
closing wall of the casing, an inlet opening in
the lower portion of the casing through which
air is delivered under pressure, an outlet open
ing for the air stream in the upper portion of 30
the casing, non-rotary deñecting vanes posi
tioned in the casing upwardly’and outwardly
from the periphery of the bowl at the outer side
of the air passage for deflecting material thrown
vthereagainst from the bowl back through the 35
air stream into the bowl, and spiral ribs carried
by the casing at the outer side of the air passage
and inclined upwardly in the direction of rota
tion of the bowl for directing material in said
passage toward the deñecting vanes.
40
5. A’mill comprising a closed casing, a grind
ing member having an upper grinding surface,
said member being mounted within the casing
for rotation about a central vertical axis, means
for rotating the member, means for introducing 45
material to be ground onto the upper grinding
surface of the member, means cooperating with
this grinding surface for grinding the material,
there being an annular air passage between the
outer periphery of the member and the enclos 50
ing wall of the casing, means for forcing air un
der pressure upwardly through the passage with
a whirling motion in the direction of rotation of
the grinding member, non-rotary deflecting
vanes positioned in the casing at _the outer side 55
of and above the air passage, means on the pe
ripheral portion of the rotary grinding member
for directing material thrown from the mem
ber toward the vanes, this material being thrown
back from the vanes onto the member„ and ribs 60
carried by the casing wall at the outer side of
the air passage and inclined upwardly in the
direction of movement of the whirling air stream
for directing material at the outer side of the
65
passage upwardly toward the vanes.
6. A mill comprising a closed casing, a grind
ing member having an upperl grinding surface,
said member being mounted within the casing for
rotation about a central vertical axis, means for
rotating the member, means for introducing ma
terial to be ground onto the upper grinding sur
face of the member, freely rotatable grinding
rollers suspended above the member in position
to be rotated by contact with the material car 75
-5
ried on thevgrixí'd'ingÍff'surface,~ there being an portion of the rotary grinding member forI di
annular air passage> between the outer periphery recting material thrown from the member toward
of the member and the enclosing wall oi the `the vanes, this material being thrown back from '
casing, an inlet opening -in the .lower portion o! the vanes onto the member, and ribs Vcarried by
the casing through which air is delivered under \ the casing wall at the outer side of the air pas‘ï
pressure', an outlet opening for the air stream sage and inclinedgupwardly in the direction o_i’
and suspended material leading from the upper , `movement o! the whirling air stream i'or- direct
portion of the casing, non-rotary deñecting vanes ' ing material at the outer side of the passage up
positioned in the casing at the >outer side of and wardly toward the vanes.
.ìoE cRn'Es. 10
m above the air passage-'manson the peripheral
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