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Патент USA US2136686

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Nov. 15, 1938.
2,136,686
H. HARDINGE
CLASSIFIER
Filed Jan. 11, 1956
4 Sheets-Sheet 1
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Nov. 15, 1938.
H. HARDINGE
2,136,686
CLASSIFIER
Filed Jan. 11, 1936
HARLOWE.
4 Sheets-Sheet 2
3mm
HARDINGE
Nov. 15, 1938.
2,136,686
H. HARDINGE
CLASS IFIER
Filed Jan. 11, 1956
45
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4 Sheets-Sheet 3
gwuc/wtm?
HAR LOWE HARDI NGE
WW ‘k. W
Nov. 15, 1938.
H. HARDINGE
2,136,686
CLASSIFIER
Filed Jan. 11, 1956
4 Sheets-Sheet 4
HARLOWE. HARDINGE
Patented Nov. is/iass
2,136,686
UNITED STATES PATENT OFFICE
2,136,686
CLASSIFIER
Ha'rlowe Hardinge, York, Pa., assignor to Hard
Y inge Company, Incorporated, York, Pa” a cor
poration voi! New Yorlr
'
Application January 11,‘ ‘1936, Serial No. 58,735
10 Claims. (Cl. 209-452)
This invention relates to apparatus of the type useful improvements in the construction, ar
used for separating various kinds of materials, rangement and combination of the several parts
and more particularly to the type of apparatus of which it is composed, as will behereinafter
‘ ‘fused- in the metallurgical and other industries for more fully described and claimed.
In the accompanying drawings:
5, classifying purposes.
Figure 1 is a vertiial longitudinal section of a
‘ More speci?cally classi?ers of the type falling
within the scope of the present invention ?nd use classi?er embodying the invention;
Fig. 2 is a transverse section taken on the line
in almost every metallurgical operation where a
mill grinds ores. The devices are also used for a _2--2 of Fig. 1, looking in the direction of the
10 great many industrial purposes and may be used
to wash sands, and other minerals. The devices
may also be used in connection with grinding
arrows;
10
‘
mills where they act in the capacity of classi?ers
Fig. 3 is an elevation of the oversize material
discharge end of the classi?er, showing the slots
in the’ portion of the screw ?ight adjacent this
which pass on as a product material of a given
end of the device; ,
15 ?neness but which returns the oversize material
for further grinding.
>‘
An object of the invention is to provide an im
- proved classi?er by which a close separation of
materials may be obtained and in which the prod
20 not is uniformly ?ne and the oversize is clean
Fig. 4 is a view similar to Fig. 3, showing the 15
slots equipped with members for varying the area
thereof;
Fig. 5 is an enlarged view. partly in section, of
a portion of the structure shown in Fig. 4;
Fig. 6 is a horizontal section taken on the line 20
in that it contains a minimum amount of ?nes
which should go out with the product.
Another object of the invention is to provide an
improved classi?er in ‘which the oversize material
25 is discharged from the main classifying chamber
with a minimum amount of wash water.
Another object of the invention is to provide an
, Fig. 7 is a section of the oversize material dis
chargelend of a classi?er having elevating ‘and
dewatering buckets; and
-
Fig. 8 is a section taken on the line B—8 of 25
Fig. 7.
- ,
improved classi?er in which the oversize mate
rial moving through the main classifying chamber
Referring to the drawings, the classi?er com
prises a main body portion or drum' II which is
preferably mounted for rotation with the axis of
30 is dewatered to a greater extent than was possible
the drum inclined with respect to the horizontal,
in prior devices of a similar nature, and in which
the water removed from the oversizematerial ad
jacent the discharge end of the main classifying
chamber can readily ?ow backwardly through
35_ said chamber without carrying with it a prepon
derance of oversize material.
Another object of the invention is to provide an
improved rotary wet classi?er in which the over
~ size material is'propelled through a main classify
40 ing chamber against a countercurrent of wash
--water by means of a screw ?ight of varying pitch
and height which squeezes the oversize material
as it approaches the discharge end of the classi
fler, and in which slots are formed in the portion
45 of the screw ?ight adjacent the discharge end of
the classi?er through which surplus-wash water
squeezed from the oversize material can readily
?ow back into the middle portion of the classify
ing chamber without carrying a preponderance
' 50 of oversize material with it.
' Another object of theinvention is to provide an
improved classi?er of the character mentioned,
which is simple in construction, and reliable and
exact in function under all conditions of service.
55
The invention also comprises certain new and
30
as shown in Fig. 1, said drum being supported on
a suitable base or frame i2.
For the purpose of rotating the drum ii, any
suitable mechanism may be utilized. In the pres
ent instance the driving mechanism is shown as 35
including an electric motor [3 which is opera
tively‘ connected through gears it, to a chain
driving means l5 of any approved construction.
For convenience the left hand end of the drum
ii, as illustrated in Fig. 1, will be referred to as 40
the front end and the right hand end of the drum
I i will be referred to as the rear end.
The right hand or rear end of the drum ii is
the end through which material to be classi?ed is
45
fed into the drum, and the left hand or front end
is the end through which the oversize material is
discharged- As shown in the present embodi
ment of the invention the axis of the drum ii is
inclined upwardly from right to left.
The material is adapted to be delivered into the
classi?er by means of a chute or trough [6 which
terminates at a suitable distance from the right
hand or rear end of the drum I l.
The right hand or rear end wall ll of the drum
50
2.
'
8,186,686
'
If is formed with
II in which 18:
mounted an annular band It.
an opening" having a discharge lip 8| for the
oversize material.
_
..
The W of the band It is to provide an
inlet opening for the classi?er, and said band is
The material discharged from, the front end of
the classi?er falls into a trough I2 and is thereby
so formed as to provide a lip over which the ?nes , carried away from the apparatus.
and water or other liquid, either as a wash or
that enters with the feed, are discharged from
the classi?er. The ?nes and water or other
liquid'discharged from the classi?er fall into a
trough 2| and are thereby carried away from the
device.
'
>
‘
Projecting through the opening til, is a pipe 23,
through which wash water is supplied to the clas
si?er.
In operation, assuming that the classi?er is
charged with material and water and the drum | I
is being rotated through the operation of the
For the purpose of conveying material from the motor it, each of the compartments 22, 24, 25, 28,
right handor feed end of the drum ||, towards ‘ 21 and 23, between the screw ?ight or helical
the left hand or front end thereof and also for trough 2|, will contain varying quantities of ma
turning the material over in the water within terial.
the drum ||, means in the form of a helical
The water line of the classi?er is normally
trough or screw ?ight 2| are provided.
above the rear discharge opening provided by the
The helical trough or screw ?ight 2| .comprises lip It, as indicated by the broken line, Fig, 1,
a metal band arranged around the inner wall of and since it is customary to have the classifier in
the drum II in thei'orm ofascrew whichisco
a slightly tilted position with the rear end lower
extensive with said drum.
than the front end, the direction of ?ow of water
The height of the metal band 2| varies from will be towards the rear end even though no
end to end, said band being of considerably less extra wash water is introduced into the classi?er
height at the right hand or feed end of the drum through the pipe 23.
_
»
| I, than at the left hand or discharge end of said
The rear end'portion of the classi?er as de?n
drum, so that the helical trough or screw ?ight by the compartments 22 and 24 and the zone
will gradually increase in depth from the rear above them, functions as a primary settling
end toward the front end of the drum II.
chamber. During the operation of the device
In order to provide for a squeezing action of the coarse or oversize material will settle in the
80 the material passing through the drum II, the bottom of the drum II, and the ?ner and other
pitch of the band 2| is varied from one end of
the drum to the other. That is to say, the con
volutions of the band 2| are so formed that the
helical trough is considerably narrower at the
85 left hand or front end than at the right hand or
rear end ofthedrum ||.
_
'
The construction and arrangement of the band
2| is such that a series of pockets or compart
ments are formed for containing the material,
40 the compartment at the right hand or rear end
of the drum || being comparatively broad in
width and shallow in depth, as indicated at 22,
Fig. 1, and the compartment 23 at the left hand
or front end of thedrum being comparatively
45 narrow in width and high in depth, and also be
ing less in cross sectional area than the com
partment 22. The intermediate compartments
24, 25, 28 and 21 progressively change in cross
sectional dimensions.
'
I
The manner in which the helical band is con
structed is clearly shown in Fig. 2, and as there
shown said band may be formed of a series of
plates cut from sheet‘ metal of suitable gauge and
fastened together and secured to the wall'of the
55 drum II by any desired means, such as welding,
riveting, or the like.
‘
Preferably the edge of the helical trough 2|
abutting the wall of the drum || should be made
integral with the wall of the drum, so as to pre
vent the passage of water and ?nes along the in
ner surface of the drum.
The portion of the helical trough nearest the
- oversize discharge end of the drum I I, is formed
with a plurality of notches 28, the purpose of
which will be hereinafter described.
' The notches 20 extend downwardly into the
helical band 2| varying distances. That is to
say, the notches 2! formed in the portion of the
helical band of greatest height are deeper with
70 respect to the height of the band than the
notches formed in saidband rearwardly of the
discharge end.
a
'
As shown in Figs. 1 and 3, the left hand or
75 front end wall 2| of the drum II is formed with
material which may have a tendency to ?oat or
is carried in suspension in the water will be car
ried out of the classi?er by the water which
passes over the lip It.
The oversize material which settles in the bot
35
tom of the drum II is forced, through the action
of the helical trough or screw ?ight 2|, towards
the left hand or discharge end of the drum, the
material being constantly turned over by the ra
tation of the drum and the action of the helical 40
trough.
‘
In its forward movement through the drum | I,
the oversize material comes in contact with
cleaner and cleaner wash water, and as the ma
terial turns'over, the ?ner particles which are
disposed between the coarser particles are liber
ated,‘ and the wash water carries these particles
of ?nes with it towards the over?ow or rear end
of the classi?er. In this way the water passing
from the front end of the classi?er towards the
rear end washes the coarse particles clean of
?nes, dirt, slimes, etc.
Due to the construction and arrangement of
the parts comprising the helical trough or screw
?ight 2|, the depth of material contained in the
successive compartments between the convolu
tions of the helical trough varies from right to
left, as has heretofore been described, so that, as
the material moves toward the discharge end of
the classi?er, a squeezing action is gradually im
parted to the material and the oversize is con
densed or compacted. This condensing of the
oversize material is effected by the elimination of
the ?ner material by the washing action and
over?ow over the top of the helical trough as the
cross section of said trough becomes smaller to
wards the discharge end 3| of the apparatus.
The purpose in so constructing the helical
trough 2| is to build up the successive masses of
material, so that when the material enters the 70
last zone, as de?ned by compartment 2!, the ratio
of water to solids therein is considerably less
than that in the rear or feed end of the classi?er.
.Another advantage resulting from construct~
ing the helical trough 2| in such a manner is
3
that the water, in ?owing from left. to right
through the drum H, is caused to pass from one
compartment to the next in a series of cascades,
Attaching elements which may be in the form
of bolts 33 are mounted in openings 38 formed in
the helical band 2| adjacent one edge of them.
and in so doing the water carries with it the
?ner material which becomes exposed as the
oversize material is turned over as it is worked
toward the discharge end.
notches 28.
As‘ shown in Fig.‘ 1, the height of the helical
trough between compartments 23 and 21 is above
in pairs, so as to receive said bolts.
the level of the water in the classi?er, so that
or slots 28 and thereby reduce the size of said 10
slots, and in order‘ to prevent an onrush of ma
terial through the slots 28 with the water ?owing
wash water ?owing from compartment 23 is
caused to fall in the'form of a cascade into com
partment 21. Furthermore, the height of the
portion of the helical trough between compart
ments 21 and 26 is considerably higher than the
height of the portion of the helical tr ugh which‘
separates compartments 26 and 25, a ‘d, there
fore, a second cascade is provided between com
partments 21 and 26.
Since the height of the helical trough becomes
' gradually lower towards the rear end .of the
classi?er, when the level of the water in the drum
II is lowered, additional cascades will be formed.
‘ Also, should the oversize discharge or left hand
end of the classi?er be‘ elevated to a position
higher than that illustrated in the drawings, this
cascading effect can be produced without de
~ creasing the amount of wash water admitted to
the classi?er, since the rear or right hand end of
the drum U will be so much lower than the left
hand or oversize discharge‘ end‘ of the drum, that
the level of the water in the drum will‘not extend
as fartcward the left as illustrated in Fig. 1,
with the result that additional portions of' the
helical trough 2| will project above the water.
Since the screw ?ight or helical trough 2|
terminates at the left hand end of the drum H,
the material will be discharged from the com
partment 23 over the discharge lip 3| and from
40 thence fall into trough 32.
The plates 34 are formed with a series of open- 5
lugs 31, and if a pair of bolts 35 are used for
each plate 34, then the openings 31 are arranged
The plates 34 are adapted to overlie the notches
therethrough, the edges of the plates 34 parallel
ing the adjacent side edges of the slots, are bent
,
outwardly, as indicated at 38.
In the drawings, the plates 34 are shown as
only partly covering or overlying the slots 28.
However, should it be desirable to nearly close
the openings through the slots, the plates can be
15
shifted further to the right, as viewed in Fig. 5, 2° ’
in which position the outwardly bent portion 38
will overlap the portion of the helical band 2| to
the right of the slots 28. Also, it will be under
stood that the openings 31 may be so disposed in
the plates 34 that said plates can be so located 25
with respect to the slots 28 as to vary the depth
of the opening of said slots, as well as the width
g th5e slots, as is illustrated by dotted lines, in
g.
.
'
'
When the oversize material is comparatively 30
coarse, obviously the plates 34 can be positioned
with respect to the slots 28 so as to permit a
considerable amount of water to flow through
theislots without carrying with it an undesirable
quantity, of material. On the other hand, the 35
?ner the oversize the more readily will it have
a tendency to ?ow back with the water. There
fore, by shifting the position of the plates 34
to restrict the opening through the slots, the’
material will be prevented from ?owing back 40
‘
with the water in objectionable quantities. .
When the classi?er is operated at normal ca
Instead of discharging the oversize directlys‘
pacity- each of the compartments between the
helical trough 2| will be ?lled with material and from the compartment 23 to the discharge lip
wash water, and since the material is squeezed or 3|, the classi?er can be formed with an enlarged
45 compacted in the several compartments by the ' discharge head 40, as shown in Figs. 7 and 8. 45
action of the helical trough, it is of advantage This dischargev head contains a plurality of
buckets 4| which function as elevators that scoop
to dewater the material as it approaches the over
size discharge end of the classi?er, so that a min
imum amount of water will pass out of the classi
50 ?er with the oversize material.
up the ‘material and deposit the same into a
the left hand portion of the helical band 2| is
formed with the series of notches 28, heretofore
referred to.
The purpose of these notches or slots 28 is to
55
chute 44.
discharge trough 42. The trough 42 extends
Therefore, according to the present invention,
permit surplus water ‘in the compacted material
in the high portion of the classi?er to drain back
into the more saturated and loosely compacted
material in the lower part of the classi?er,
60
‘
It will be noted by referring to Fig. 1, that the
last ?ight to the left of compartment 23, is much
downwardly through an opening 43 in the outer 50
end wall of the head 40 and terminates over a
-
The left hand or front end of the drum ||
opensv directly into the head 40. The helical
trough 2| terminates adjacent to the junction 55
of the drum II with the head, so that the ma
terial, in moving forwardly through the drum | |,
is forced by the last ?ight 45 into the bottom
of the head 40.
The buckets 4| may be so constructed that 60
the material deposited in the bottom of the head
40 is readily picked up and carried upwardly to
a point above the level of the water in the classi
higher than the discharge lip 3|, so that the
oversize will be forced out a large part of the
revolution of the drum ll, rather than at only ‘ fier whereby the water quickly ‘drains from the
elevated material before such material is dis- 65
65 one point. The water in the material being dis
charged drains back into the drum through the charged from the buckets.
As shown in Fig. 7 the feed water pipe 33 may
slotted openings 28, and if so desired the area
of these openings can be varied or adjusted to terminate in the discharge head 48. However, it
should be noted that when so desired, said pipe
suit varying conditions and various kinds of ma
can extend through the head 40 and terminate 70
70
As'shown in Figs. 4, 5 and 6, one manner of in the main classifying chamber of the drum ||.
adjusting the sizes of the slots 28 is to employ an The point at which the feed water pipe 33
terminates depends entirely upon the kind of ma
adjustably mounted plate 34 for each slot.
terial being classi?ed. Thus, should the ma'-'
The plates 34 are preferably formed of 2. rec
terial delivered to the discharge head 40 from the. 75
tangular piece of sheet metal or plate steel.
terial.
75
'
'
~
-
4
main classitying chamber contain an undesirable
quantity oi’ slimes, dirt,_etc., it will be advan
tageous to deliver the wash water into the dis
charge head 40, so that the oversize material
will be further cleansed. On the other hand.
should the .oversize' material being discharged
trom the drum H into the head 40 be com
‘ paratively clean, and require no further washing,
then the water pipe 33 can extend through the
10 head 40 and terminate over compartment 23, as
shown in Fig. 1. In this case the oversize ma
terial in the head 40 will be substantially de
watered, since very little wash water will ?ow
therewith past the end 45, on account of the
15 drains provided by the slots 28 and the dam e?ect
oi.’ the successive compartments.
Having thus described my invention, what I
claim is:—
1. A classi?er comprising a rotatable classify
ing chamber having end walls, a ?nes discharge
opening in one end wall of said chamber, an
oversize material discharge opening in the oppo
site end wall of said chamber, and a helical band
disposed around the interior of said chamber for
moving material towards said oversize discharge
opening, said band decreasing in pitch and in
creasing in depth from the ?nes discharge end
toward the oversize discharge and of said cham
ber, the decrease in pitch of said band being at
a greater rate than the increase in depth with
respect to the volume, whereby the net volume
of material carried by the band constantly de
creases and is zero where the band terminates
at the oversize discharge end wall of the chamber.
2. A device of the class described comprising
a rotatable drum having an impervious wall, a
helical trough ?xed to the interior of the drum
and adapted to prevent the passage oi.’ water and
other matter along the inner surface 01' the drum,
40 the height oi’ said trough gradually increasing
from one end of the drum towards the other,
means for supplying wash water to the drum,
and notches formed in the highest portion of
said trough, said notches extending downwardly
of the trough varying distances, the notches in
the portion of the trough of greatest height be
ing deeper with respect to the height of the
trough than the depth of the notches formed in
said trough rearwardly of the end of the drum,
50 whereby liquid in the material in the highest
end through which ?nes and liquid are dis
charged, an opening at the front end of the
drum through which oversize material is dis
charged, a helical band extending through the
drum and adapted to prevent’ the passage of
liquid along the inner surface of the drum, said
helical band being adapted to convey material
delivered into the rear end of the drum toward
the front end thereof, means for supplying liquid
to the drum. said helical band gradually in 10
creasing in depth from the rear end towards the
front end of the drum, the portion or said band
adjacent the rear end or the drum being sub
merged by liquid in the drum, the portion of the
trough adjacent the front end of the drum ex 16
tending above the liquid in the drum, said drum
having an impervious wall, and means for drain
ing liquid from material in the portion of the
helical band adjacent the front discharge end
01' the drum back towards the rear discharge end 20
of the drum comprising notches formed in the
portion of said band adjacent the discharge end
of the drum, said notches extending downwardly
into the band, varying distances, the notches
formed in the portion 01' the bond of greatest 25
height being deeper with respect to the height of
the hand than the notches formed in said band '
rearwardly or the discharge end of the drum.
5. A classi?er comprising a rotatable drum
having a fines and liquid discharge opening at 30
one end and an oversize discharge opening at
the opposite end, a helical band for moving ma
terial through the drum from the ?nes discharge
end towards the oversize discharge end of the
drum, means for supplying liquid to the drum, 35
and openings formed in the helical band adja
cent the oversize discharge end of the drum for
draining liquid from compartments between said
band back towards said ?nes discharge end, said
openings extending downwardly into the helical 40
band varying distances and terminating above
the wall of the drum, the openings formed in
the portion of the helical band adjacent the over
size discharge end of the drum being deeper with
respect to the height of said band than the open 45
ings formed in said band rearwardly of the over
size discharge end.
6. A classi?er comprising a rotatable classify
ing chamber having end walls, a ?nes and liquid
discharge opening in one end wall of said cham 50
ber, an oversize discharge opening in the oppo
site end wall oi’ said chamber, said chamber hav
portion of the trough can drain backwardly to
wards the opposite end of the drum.
3. A device of the class described, comprising a a ing an impervious outer wall, a helical band dis
rotatable drum having an impervious wall, means posed around the interior of said chamber for
for supporting the drum in a position tilted from moving material towards said oversize discharge
the horizontal, means for rotating said drum, a opening, said band being adapted to prevent
screw ?ight ?xed to the interior of the drum the passage 01' liquid along the inner surface of
and adapted to prevent the passage oi.’ liquid said chamber, said band decreasing in pitch and
along the inner surface of the drum, the pitch increasing in depth from the ?nes discharge end
60 of said screw ?ight at the lower portion of the
towards the oversize discharge end of said cham
drum being relatively steep for rapidly advanc
ber, the decrease in pitch oi’ said band being at
ing material toward the upper end of the drum a greater rate than the increase in depth with re
when the drum is rotated, and notches in one spect to the volume, whereby the net volume
end portion or the screw ?ight for draining of material carried by the band constantly de
liquid in the portion of the drum at the upper creases and is zero where the band terminates at
end thereof back towards the lower portion of said oversize discharge and wall of the cham
the drum, said notches extending downwardly ber, and notches formed in said band adjacent
into the screw ?ight varying distances, the the discharge ‘end of said chamber for draining
notches formed in the portion of the screw ?ight liquid from the material, said notches extending
of greatest height being deeper with respect to downwardly into the helical band varying dis
the height of the screw ?ight than the depth of tances, the notches formed in the portion of the
the notches formed in said screw ?ight rearwardly helical band of greatest height being deeper with
' of the upper end of the drum.
respect to the height of the band than the notches
4. A device of‘the class described comprising a formed in said band rearwardly oi.’ the oversize
75 rotatable drum having an opening at its rear discharge end of said chamber.
60
65
70
75
2,186,686
'I. A classi?er comprising a rotatable classi
lying chamber having end walls, a helical band
mounted in said chamber and adapted to pre
vent the passage of liquid along the inner sur
face of the chamber, said chamber having im
pervious walls, one of said end walls having a
?nes discharge opening formed therein, an open
ing formed in the opposite end wall through
which the oversize material is discharged, an en
10 larged head attached to the oversize discharge end
or said chamber, means in said head for elevating
the material delivered thereto from said cham
ber and for discharging the same from the clas
si?er, the oversize discharge opening being great
15 er in diameter than the internal diameter of said
band at the point where said band terminates ad
j acent to said oversize discharge end of saidcham
her, the convolutions of said band varying from‘
the ?nes discharge end towards the oversize dis
20 charge end, whereby the net volume of material
carried by the band constantly decreases, means
for feeding material and liquid into said cham—
her, and notches formed in the portion of said
band of lesser volume for draining liquid from
25 the material back towards said ?nes discharge
end of the classi?er, said notches extending
downwardly into the band varying distances, the
notches in the end portion or the band being
deeper with respect to the height of said band
and all of said notches terminating above the
wall of said chamber.
.
8. A classi?er comprising a rotatable drum
mounted on an inclined axis and having annular
40
end walls providing central openings for the
drum, the opening in the lower end wall serv
ing as a ?ne material discharge opening and
the opening in the upper end wall serving as an
oversize material discharge opening, and a hell
cal band disposed around the interior of the drum
for moving material towards the oversize dis
charge opening, said band extending the entire
length of the drum and terminating in contact
with the upper end wall of the drum, said band
decreasing in pitch and increasing in depth from
the ?nes discharge end toward the oversize dis
charge end of said drum, said oversize discharge
opening being greater in diameter than the open
ing through the band at the discharge end oi’ the
drum
5
‘9. A classi?er comprising a rotatable drum
mounted on an'inclined axis and having annular
end walls providing central openings for the
drum, the opening in the lower end wall serving
as a ?ne material discharge opening and the
opening in the upper end wall serving as an
oversize material discharge opening, a helical
band disposed around the interior of said drum
for moving material towards said oversize dis
charge opening, said band extending the entire 10
lengthvof the drum and terminating in contact
with the upper end wall of the drum, the band
increasing in depth from the ?nes discharge end
toward the oversize discharge end of the drum,
said oversize discharge opening of the drum 15
having a diameter greater than the diameter
of the opening through the band at the over
size discharge end of the drum, meanstor sup
plying liquid to the drum, and openings formed
in the sections of the band adjacent the discharge 20
opening for draining liquid from material back
wardly towards the opposite end of the drum.
10. A device of the class described comprising
a rotatable drum mounted on an inclined axis
and having annular end walls providing central 25
openings for the drum, the opening in the lower
end wall serving as a ?ne material discharge
opening and the opening in the upper end wall
serving as an oversize material discharge open
ing, a helical band ?xed to the interior of the 30
drum and adapted to prevent the passage of
water and other matter along the inner surface of'
the drum, said band extending the entire length
of the drum and terminating in contact with the
discharge end‘ wall of the drum, the height of 35
said band gradually increasing from the ?nes
discharge end towards the oversize discharge end
of the drum, means for supplying wash water to
the drum, and notches formed in the oversize
discharge end portion of said band, said notches
extending downwardly into the band and ter
minating above the inner surface 01' the drum for
draining liquid vfrom the material in the portion
of the band adjacent the oversize discharge end
oi’ the drum backwardly towards the opposite end 45
of the drum.
HARLOWE HARDINGE.
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