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Патент USA US2126081

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Aug. 9, 1938.
E. G. BAILEY ET AL
2,126,081
PULVERI ZER
Filed March 23, 1934
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Patented Aug. 9, 1938
2,126,08l
UNITED ‘STATES
PATENT OFFICE '
2,126,081
PULVERIZER
Ervin G. Bailey, Easton, Pa., and Ralph M. Hard
grove, West?eld, N. J., assignors to The Bab
cock & Wilcox Company, Newark, N. J., a cor~
poration of New Jersey
Application March 23, 1934, Serial No. 716,936
4 Claims. (01. 83-45)
Our present invention relates to apparatus for grinding capacity. This undesirable distribution
pulverizing materials, such as coal, cement, rock
products and ore, and more particularly to pul
verizers wherein the material to be pulverized
5 passes through a plurality of successive grinding
stages, each formed by a pair of Vertically spaced
of the grinding load naturally results in a de
crease in the degree of ?neness of the product.
As pulverizers of the character described are nor
mally associated with classifying apparatus for
relatively rotatable grinding rings between which
separating and returning the coarse particles to
the pulverizer, the amount of coarse particles
is positioned an orbital row of rolling grinding
returned correspondingly increases, with a corre
elements.
sponding increase in the cost of grinding per ton
of product of the desired degree of ?neness.
The rate of passage of the material through the
upper grinding stage, and thereby the depth of
material therein and the amount of the circulat
ing load, may be controlled by providing flow re
stricting means at the outer or discharge side of 15
In operation the grinding elements
move over the surface of the grinding rings and
eifect a grinding action on any material between
the contacting surfaces. When the relative
movement between the grinding‘ parts is pro
duced by having the lower grinding ring rotary
15 and the upper grinding ring non-rotary, the ma
terial undergoing pulverization is advantageously the upper grinding stage, as disclosed, for ex
supplied to the inner side of the row of grinding ‘ ample, in, our prior joint patent with Perry R. ‘
,
‘
elements and passed outwardly therethrough. Cassidy, No. 2,071,379. ,
The outward flow of material may be partly due
Heretofore, as shown in our said prior patent,
20 ‘to a head of material at the inner side ofthe
such flow controlling provisions have consisted 20
row, but is mainly due to the centrifugal effect
exerted on the material by the rotation of the
lower grinding ring, over the upper surface of
which the material passes, and the grinding ele
25 ments,‘ and to the displacement effect of the roll
ing grinding elements on some of the material in
their path of rotation. At economical speeds, the
combined effects normally result in a too rapid
of an annular basket or plate forming a restrict
flow of material across the grinding area.
In a multi-stage pulverizer, in which the grind
ing stages are vertically spaced and formed by
top, intermediate and bottom grinding rings be
tween the successive pairs of which are respec
tively positioned upper and lower circular rows
35 ‘of metallic grinding balls having a relative rota
tion with respect to the grinding rings contact
ing therewith due to a ?oating drive connection
to the intermediate ring, thelmaterial passes out
“ 40
ed annular gap with the rotary intermediate ring
in the path of flow of the material passing from
the upper grinding stage to the lower stage. Such
means have been found objectionable because of 25
their inherent inability to maintain a uniform
?ow controlling effect for an extended period of
operation and the tendency of the material to
pack at the gap. This lack of'uniformity of con
trol is mainly due to changes in position of the
intermediate ring relative to the gap forming
provisions with wearing of the lower grinding
ring and balls and Wear on the gap-de?ning edge
of the basket or ledge plate due to friction of the
material, which is increased by the rotation of
the adjacent intermediate ring. The variations
in size of the flow controlling gap due to these
various causes may be somewhat offset by read
wardly through the upper grindingv stage and
justing the position of the gap-forming provi
inwardly‘ through the lower stage; The mate
sions.
rial tends to pass at a higher speed through the
upper grinding stage due to the centrifugal force
imposed thereon in that stage, while the cen
trifugal effect, if any, on the material in the low
45. er stage will oppose its passage therethrough.
The depth of material in a grinding stage of the
character described is an important factor af
fecting the amount of grinding accomplished
therein, as little, if any, grinding will be done on
50 the upper ring of the stage if the depth of mate
rial falls below a certain value. Thus with a too
rapid flow of material through‘the upper grind
ing stage, those grinding parts will do less grind
ing than they are capable of doing, while the
55 lower grinding stage will be loaded beyondv its
The proper adjustment however cannot
be accurately determined without interrupting
the operation of the pulverizer, and moreover is
limited in extent.
,
,
,
'
The general object of the present invention is
the provision of pulverizers of the character de
scribed with improved provisions for controlling
the ?ow therein of material undergoing pulveri
zation. A more speci?c object is the provision of
pulverizer ?ow controlling means which will
maintain a uniform flow controlling effect re
50
gardless of changes in size or position of the
grinding parts and are not subjected to undue
wear in operation. A further speci?c object is
the‘provision of a ?ow controlling dam on a pul
verizer rotary grinding ring having an outward 55
2
2,126,081
flow of material thereon so constructed and ar
ranged relative to the grinding area on the ring
to substantially neutralize the centrifugal effect
thereof on the material undergoing pulverization.
A further speci?c object is the provision of a
multi-stage air-swept pulverizer of the general
character described having a flow controlling dam
on the intermediate rotary ring thereof associat
ed with means for facilitating the separation of
1 O ?nes before the material reaches the classi?er.
The various features of novelty which charac—'
terize our invention are pointed out with par
ticularity in the claims annexed to and forming
a part of this speci?cation. For a better under
standing of the invention, its operating advan
tages and speci?c objects attained by its use, ref
erence should be had to the accompanying draw
ing and descriptive matter in which we have
row of balls into the lower or discharge section
of the casing, to which a discharge conduit 45 is
connected.
The discharge of the material is
facilitated by a series of sweep blades 46
mounted on the drive yoke 31.
In accordance with our present invention, de
sirable grinding conditions are continuously
maintained in each grinding stage with high
capacity operation and low power consumption
by employing flow controlling or load distribut
ing provisions which are constructed and ar
ranged to function uniformly in operation over
a prolonged period.
One of the novel features of our flow control
ling provisions is their arrangement on and ro
' lustrated and described various embodiments
tatable with the intermediate ring 32, whereby
of our invention.
the troubles heretofore due to wear on the sta
'
Of the drawing:
tionary ledge plate in proximity to the rotary
Fig. l is a sectional elevation of a gravity dis
charge pulverizer incorporating our invention;
Fig. 2 is an elevation and Fig. 3 is a plan view
of the adjustable skirt shown in Fig. 1; and
Fig. 4 is a fragmentary view illustrating a modi
?ed dam construction.
The gravity-discharge type pulverizer illus
trated in Fig. 1 comprises a metallic casing 30
.having a cylindrical upper section enclosing the
‘material pulverizing parts which include a non
rotary top grinding ring 3], a rotary intermediate
grinding ring 32, and a non-rotary bottom grind;
ing ring 33 spaced vertically in the casing, a cir
; ‘cular row of rolling grinding elements, prefer
ably in the form of heavy metallic balls 34, be
tween the top and intermediate grinding rings
and a concentric row of grinding balls 35 between
the intermediate and bottom grinding rings. A
40 floating drive connection for the intermediate
grinding ring from a main drive shaft 36 axially
ring will be eliminated. In the drawing we have
illustrated various forms of flow controlling pro
visions of this type.
The flow control provisions consist of means 25
forming an adjustable dam on the periphery of
the rotary intermediate ring 32, and are based
upon our theory that there is a slope correspond
ing to the speed of the intermediate ring and
coe?icient of friction of the material undergoing
pulverization, on which the particles of material
will be in equilibrium with the component forces
of gravity and friction balancing the component
of centrifugal force. Under such conditions, the
flow of material over the top of the dam will be 35
due to the push or displacing effect thereon of
the balls 34 and the discharge of material will
increase as the level in the grinding zone tends to
build up.
end of the drive shaft and having driving arms'
If the dam slope be too low the material will 40
?ow at too great a rate, and if too high the mate
rial will be retained in the top ring for too long
a period, and thereby lower the capacity, in
crease the power consumption of the pulverizer,
38 thereon each positioned between andverti
cally movable relative to a pair of plates 39 on
and throw an excessive amount of the grinding 45
load on the upper row of balls tending to cause
arranged relative to the ball rows is effected
through a drive yoke 37 mounted on the upper
the inner side of the intermediate grinding ring.
Similar parts provide a ?oating non-rotary con-7
nection between the top grinding ring and the
casing 30, as shown. The adjacent faces of the
several grinding rings are formed with races or
tracks along which the corresponding rows of
balls move. A substantial grinding pressure is
ordinarily applied to the upper side of the top
grinding ring 3| by a series of helical pressure
springs 46 arranged in a circular row on the top
grinding ring, as indicated in Fig. l. The spring
pressure is externally adjusted in accordance
with the hardness of the material undergoing
(30 pulverization. The material to be pulverized is
delivered to the upper part of the casing through
one or more feed spouts 42 projecting through
the casing top plate 4|.
' .
The feed spouts 42 deliver the material cen
trally of the top grinding ring, Where‘it is di
rected to the inner side of the upper row of balls
34 by a conical cover plate 43 mounted on the
intermediate grinding ring. The material will
pass substantially spirally outward on the inter,
70 -mediate grinding ring and through the upper
row of balls, and is pulverized thereby. The
material pulverized in the upper grinding stage
drops to the outer side of the lower row of grind
Ci
inwardly through the lower row of balls 35. The
material is further ground in the lower grinding
stage and drops from the inner side of the lower
ing balls. The partly pulverized material drop
‘;ping to the lower'grinding stage is fed by gravity
the material to pack therein.
In the construction illustrated in Figs. 1 to 3,
the dam is formed by a cylindrical ledge plate 57
mounted on the periphery of the intermediate 50
ring and carrying an adjustable skirt section 58
formed by a plurality of overlapping curved
plates 59, each of which is provided with verti
cally elongated slots 69 through which project
bolts 6| carried by the ledge plate 51. The ad-
_
justable skirt section is held in any of its posi
tions within its range of adjustment by curved
washers 62 and nuts 63 carried by the bolts.
The raising or lowering of the skirt correspond
ingly varies the effective angle of the dam rela
tive to the grinding race. With this arrangement
a ledge plate of a height corresponding to the '
minimum angle calculated may be mounted on‘
the intermediate ring and the most desirable
angle within that range determined experimen
tally by varying the height of the skirt. Small
variations in the height of the dam have been‘
found to cause substantial variations in the pul
verizer capacity, ?neness-of the output, and
power consumption. For example, an increase 70
in height of the dam of approximately two
inches was found to substantially lower the ca
pacity and ?neness of the product and increase
the power consumption 40% as compared with '
the results obtained with the lower height. The 7511.:
3
2,126,081
cylindrical ledge plate 51 may be detachably
inner side of said row of elements, a circular ledge
mounted on the grinding ring, as in Figs. 1 to 3,
or integrally formed thereon as shown in Fig. 4.
With the various forms of flow controlling pro;
visions disclosed, the pulverizing load will be de~.
sirably distributed so that under varying load
conditions, the depth of material in the upper
grinding stage will remain substantially the same.
By this arrangement, a substantially uniform. and
10 predetermined grinding effect will be given to the
material in the upper grinding stage, and a fur
ther grinding supplied in the lower stage.
The
grinding load in the several stages can be thus
proportioned so that none of the stages will be
15 overloaded with a consequent decrease in the
degree of ?neness of the product and increase in
circulating load, or underloaded with a conse~
quent decrease in pulverizer capacity and in~
creased wearing or‘ the grinding parts.
While in accordance with the provisions of the
20
statutes we have illustrated and described herein
the best forms of our invention known to us,
those skilled in the art will understand that
changes may be made in the form of the appa
25
ratus disclosed without departing from the spirit
of the invention covered by our claims, and that
certain features of our invention may some
times be used to advantage without a correspond
ing use of other features.
We claim:
30
1. A pulverizer comprising a casing having an
inlet for material to be ground and an outlet for
ground material, a grinding stage having an out
ward ?ow of material therethrough and including
an upper grinding ring, a rotary lower grinding
ring movable relative thereto, and an orbital row
of rolling grinding elements positioned between
said grinding rings, means for supplying material
to be ground to the inner side of said row of ele
40 ments, means forming an annular dam, on said
rotary grinding ring at the outer side of and ex
tending above the centers of the elements in said
row, said dam being radially spaced throughout
its height from said vrow of elements, and means
45 for varying the effective height of said dam to
regulate the discharge and ?neness of the mate
rial leaving said grinding stage including a sec
tional skirt forming the upper portion of said
dam, and means for varying the position of said
50 skirt.
2. A pulverizer comprising a casing having an
inlet for material to be ground and an outlet for
ground material, a grinding stage having an out
ward ?ow of material therethrough and includ
ing an upper grinding ring, a rotary lower grind
ing ring movable relative thereto, and an orbital
row of rolling grinding elements positioned be
tween and contacting with said grinding rings,
means for supplying material to be ground to the
plate on the periphery of said rotary grinding ring
forming a circumferential dam on said rotary
grinding ring at the outer side of and radially
spaced throughout its height from said row of "It
elements, and means for varying the height of
said dam to regulate the amount and ?neness
of the material discharging from said grinding
stage including an upper skirt section adjustably
10
mounted on said ledge plate.
3. In a pulverizer comprising a casing having
an inlet for material to be ground and an outlet
for ground material, an upper grinding stage
having an outward flow of material therethrough
and including a rotary grinding ring and an or
bital row of rolling grinding elements positioned
thereon, a lower grinding stage receiving material
discharging from said upper grinding stage,
means for supplying material to be ground ‘to the
inner side of said row of elements, an adjustable
flow controlling dam mounted on said rotary
grinding ring at the outer side of and radially
spaced throughout its height from said row of ele
ments, and means for varying the effective height
of said dam for regulating the amount and ?ne 25
ness of the material delivered to said lower grind
ing stage including a sectional skirt forming the
upper portion of said dam, and means for vary
ing the position of said skirt.
4. In a pulverizer comprising a casing having 30
an inlet for material to be ground and an outlet
for ground material, an upper grinding stage hav
ing an outward ?ow of material therethrough and
including a non-rotary top grinding ring, a ro
tary intermediate grinding ring movable relative
thereto, and an orbital row of rolling grinding
elements positioned between said top and inter
mediate grinding rings, a lower grinding stage
receiving material discharging from said upper
grinding stage and having an inward ?ow of ma
40
terial therethrough and including said rotary in
termediate grinding ring, a non-rotary bottom
grinding ring, and an orbital row of rolling grind
ing elements positioned between said intermediate
and bottom grinding rings, means for supplying
material to be ground to the inner side of said
upper row of elements, a circular ledge plate on
the periphery of said rotary grinding ring forme
ing a circumferential dam on said intermediate
grinding ring at the outer side of and radially 50
spaced throughout its height from said upper row
of elements, and means for varying the height of
said dam to regulate the amount and ?neness of
the material delivered to said lower grinding
stage including an upper skirt section adjustably 55
mounted on said ledge plate.
ERVIN G. BAILEY.
RALPH M. HARDG'ROVE.
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