Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the production of metal
strip or sheet and more particularly to the compaction of
particulate metalliferous material into strip or sheet
form ~hereinafter referred to simply as strip)e
More especially, but not exclusively3 the invention
relates to the roll compaction of metallic powder
into strip. The term "metalliferous material'l as used
herein includes metals, metal containing and metal bearing
; , materials.
L0 Conventionally, a compaction mill includes a pair
of rolls mounted with their rotational axes spaced in
a substantially horizontal plane to define a roll gap
therebetween;~particulate material,,eg. metal,powder,
is fed into the mill from a hopper mounted with its
15 , discharge orifice positioned above the roll gap of
the mill. To confine powder to~the roll ga~p it is necessary
to seal the spacing between the ends of the rolls.
Previous proposals for sealing these spaces have
included use of endless belts which frictlonally engage
the opposed end surfaces of the rolls from points above to
the bottom of~ the roll gap., The belts extènd into openings
formed in the end walls o the hopper and an adiustably
mounted strip~is located within each opening to regulate
the surface area of belt in contact with the powder within
the hopper. ~Other proposals or sealing the ends of the
roll gap have included the use of rolls provided wi~h
overlapping flanges at their ends and discs rotatable so
that ~heir ~peripheries engage the opposed,~end surEaces of
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the rolls in the region of the roll gap~
These proposals all suffer from the disadvantages
that ~he belts~ flanges or rotating discs tend to draw
incrcasingly excessive amounts of powder into the end
zones ofthe roll gap as the rolling speed of the mill
increasest The rate at which powder enters the roll
gap is consequently not uniform across the length of
the roll gap which leads ~o strip ~eing produced of
uneven ~hickness and density. In extreme cases the
increased flow of powder to the end zones of the
roll gap can resul~ in roll failure due to the high
local pressures generated.
The presence of the previously mentioned adjustable
strips to reguLate the surface area of belt in contact
lS wi~h the powder in the hopper only partially alleviates
~: the problem of ~increased powder flow into the end zones
; ~ of the roll gap since even~relatively a small surface
: . area of belt exposed to the pow~er draws powder into the
~: - roll gap end zones~at a significa~tly greater rate than
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flows by gravity into the roll gap intermediate the end
zones. In consequence, the edges of the strip emerging
from the compaction mill are of increased density thus
necessitating trimming to a~hi_ve the required consistent
. density:and~thickness across the width of the stripO
25 ~ According to the present invention in one aspect,
there is provided apparatus for compacting ~particulate
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z ~. metalliferous materLal into strip orm whLch comprises
~: ~ a pair of compaction rolls mounted with their rotational
axes spaced in~a substantially horizontal plane to define-
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a roll gap therebetween~ movable endless belts positioned
one at each end of the roll gap in engagement with the end
faces of the rolls to close off the ends of the roll gap, a
hopper for feeding particulate ma~erial to the roll gap
mounted with its discharge orifice positioned above and
extending across substantially the full length of the roll
gap, shielding plate assemblies positioned one behind or in
front of each side wall of the hopper, means for effecting
relative movemen~ between the shielding plate assemblies and
the hopper side walls whereby the lower margin of each
shj~elding plate assembly can protrude at least partially
below the lower margin of the respective hopper side wall
to define the l.engthwise extending boundaries of the discharge
orifice of the hopper, and means for restricting the flow of
particulate material to the end zones of the roll gap to .
counteract the tendency of particulate material to be drawn
into these end zones by the endless belts thereby to maintain
the rate at which particulate material enters the roll gap
substantially uniform along Lts entire lengthD
~ In a preferred arrangement~ the lower margins o the
hopper side walls and shieldi~g plate assemblies are so
shaped that together they define lengthwise extendi.ng
discharge ori~fice bound~ries which protrude dow~wardly at
their ends to restrict flow of particulate material to the
25 . end zones of the roll gap. The lower margin of each
shielding plate assembly may be symmetrically shaped about
its mid-point to define downwardly protruding end portions
and the lower margins of the hopper side walls may lie in
: a common substantially horixontal plane or vice versa. The
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hopper side walls may carry flexible extensions which
engag~ the barrel surfaces of the rolls.
Preferably, the shielding plate assemblies are
slidably mounted behind the hopper side walls~ Means may
additionally be provided for raising and lowering the
hopper relative to the roll gap~
In one embodiment of the invention, each shielding
plate comprises a flat plate of width substantially equaL to
that of its respective side wall. In an alternative
embodiment each shielding plate assembly comprises a pair
of downwardly extending strips which are movable to protrude
below the lower margin of the adjacent side wall at the ends
thereof.
In an alternative construction, surfaces of each
hopper side wall and/or shielding plate assembly which lie
abo~e the end zones of the roll gap are roughened or coated
with a high friction material to resist the flow of particulate
-~ material to~ the end zones of the roll gap!
The surface;area of each endless belt in contact with
20 ; the particulate material in the hopper may be varied by means
of an adjustably mounted shutter provided with a high
Eriction surface. Alternatively, each adjustably mounted
shutter may~have a surface whîch protrudes into the space
- immediately above one end zone of the roll gap to restrict
~5 flow of particulate material into said end zone,
According to the present i~vention in a further aspect9
~; ~ a ~ethod of producing strip by compacting particulate
metallierous materlal comprises the steps of feeding
particulate material into a roll gap defLned between a
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pair of compaction rolls mounted with -their rotational axes
spaced in a substan-tially horizontal plane, closing off the
ends of the roll gap by means of endless belts positioned one
at each end of the roll gap in engagement and moveable with the
end faces of the rolls, controlling the rate of feed of
particulate material to the roll gap by varying the area of roll
surface exposed to the particulate materiaI, and restricting the
flow of particulate material to the end zones of the roll gap to
counteract the tendency of particulate material to be drawn into
these end zones by the endless belts thereby to maintain the
rate at which particulate material enters the roll gap substan~
tially uni-form along its entire length. In a still further
aspect, the invention relates to strip produced in accordance with
the method set out in the preceding sentence.
The flow properties of the particulate material
within the hopper may be varied differentially across the length
of the hopper b~ suitable addition of a solid (eg. graphite),
li~uid (eg. oil or water) or gaseous agen-t.
In a still further aspect, the invention provides
apparatus for compacting metallic powder into strip form which
comprises a compaction mill, movable endless belts positioned
one at each end of the roll gap of the mill in frictional
engagement with the end faces of the mill rolls to close off the
ends of the roll gap, a powder feed hopper mounted with its
disaharge orifice~positioned above and extending across
substantially the full length of the roll gap of the mill,
shielding plate a~ssemblies positioned one behind each side wall
of the hopper and movable relative
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thereto to positions in which they at:least partially
protrude below the lower margin of the hopper side walls
to define the lengthwise extending boundaries of the
discharge oriEice of ~he hopper, and means for restriot.ing
the flow of powder to the end zones of the roll gap to
counteract ~he tendency of powder to:be drawn into these
end zones by relative movement~between the endless belts
and powder entering~the roll-gap..~:~
In a prèferred use of the apparatus an.d operation
L0 of the method describ d above, the particulate material
consists of metallic powder, eg~ iron, mild~or stainl.ess
steel, nickel, copperj alt~ninium,-:or metalliferous ore~
The powder may be produced b~ a~water: atomisation teehnique~
The invention will now be described by way of example
with referenceito thle accompanyLng~diagrammatic drawings
- . in which~
Figure~l is a side.elevationa-l view in section of
~ . apparatus in accordance~.with the:invant.ion,
: . Figure~3 is.a :side elevationaI view of an edge belt
and sh~tter assembly used ~o.retain metal:powder within
the sides of the roll gap of the m~ll illustrated in Figure
~-Figures:3a~and 3e are.front elevational views of
hopper sidè;wall~s and associated shielding plate assemblies
employed in:the milll illustrated in Figure 1,
Flgures.4a~and 4b illustrate alternative hopper side
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wall and shielding~plate assemblies t:o those illustrated
in Figures 3a to :3e~
Figure~ S shows~a ront elevational view of an
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alternative shielding pla~e assembly in acc~rdance with
the inventiong and
Figures 6a ~nd 6b are respectively plan and side
viewsofan alt~rnative form of shutter assembly to that
lllustrated in Figure 20
The invention will be described with reference to
the production of metal strip by roll compacting metal
~eg, s~eel3 powder produced by a water-atomisation technique.
Where ~ppropriate9 throughout the following description,
like integers bear the same reer~nce ~umerals.
The comp~ction mill illus~rated in Figure 1 includes
a pair of ~.o-operating contra-rotatlng rolls 1,2 which
toge~her de~ine a roll gap 3 and which are mounted wlth
their rotational axes ~paced apart in a substantially
hori~on~al pl~neO The roll gap 3 may be varied by movement
o~ one roll ~ow~rds or away from ~he other in a known mannerO
A hopper 4 iæ moun~ed ~bove the roll~ 1,2 to feed metal
powder P lnto~the roll ~ap 30 TEIe hopper 4 comprises end
wall~: S betwe~n w~lch ~re mount~d ~w~ in~ardly inclined
side wall~ 6 carIying 1exible extensions 7 which project
pàrt-w~y in~:o the entry portloTI of ehe roll gap ~, Positioned
b~hind e~ch hopper side wall 6 is a shielding plate assemb:Ly
8,. Thése shie:Lding pl~te ~emblies 8 ~nd he flexible
extersion~ 7 o ~he hopper sld~ W~ 9 6 ~r~ pre~erably
m~nufactured from ~pringy m~tal ~nd ~re cur~ed particularly
at their ~ow~r end~ ~o ~hat they eng~ge th~ barrel sur~aces
of th~ rolls 1,~2 1~:the vicini~y of the roll ~ap 3 .~T~e
: ~hL~lding plate ~:s~mbl~ies B~nd th~ xibiè extensions
o ~he s~de wall~ ~oge~er ~eLne th~ g~hw~se extending
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boundaries of a slot 9 through wh~ch powder P presen~ in
the hopper 4 is ed into the roïl g~p 3~, The slot 9 ex~ends
over the ful 1 1 eng~h o ~ the rol 1 ~ap 3 .
Thc hopper 4 is orned at its uppe~ end with flanges
11 which extend outw2rdly to positions above the roll
chocks 12. Hydraulic jacks 13 are pos~tioned between
the opposed sur~ace~ of the fl~nge~ 11 and chocks lZ and
~re operable ~o move the hopper 4 towards or away fr~m
the rol 1 gap 3 ~,
1() Each shleldlng plnte assembly 8 i8 slidably mo~m~ed
at lts uppe~ end with:Ln a ~ide 14 sectlred ~o a side face
o one of ~he roll chocks 12. l'he shielding plate assemblies
8 can be moved into, or out o, the roll gap 3 by means of
a motor (not . s,lown) mechanically couple~ to t4e assemblies
8, The width o~ the slot 9 and th ex~ent of roll barrel
sur~ce ex~posed ~o the powde~ can thereby be altered to
~ry~ t:he ra'c~ a'c ~qhi~h powder i8 fed into the roll gapG
As shown in E~i~re 2~ the end~ of ~he roll gap 3
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are closed by en~les~ belts 18 whlch track around idle
20 . pulley~ 19 and fri~tio~ally eng~ge ~he opposed end faces
o~ th2 rolls 1, ~`in the vicin~ty o~ ~heiroll gap. Sufficlent
drive may be applied ~o the belt6 to overcome the mechanical
re~istanc~ o~ ~ the p~lleys ~nd ~o ensure tha~ ~h~ speeds o
the b~lts a~e matched to the speeds of l:he rollæ~ Each
h~lt 18 i~ urged by its sespective lower pulley 1 9a 1nto
cohtacJc with on~ p~ir of e~d faces of the rolls 1,2 between.
~ po~ ons ~b~ve~ and 1ust b~low the bottom of the roll gap
: . : 3: so ~ ~o ~eal off ths ends o ~he roll g~p.~ ~n adjus~able
~ . skid 20 i2 p~vid2~ to ~a.lntain tigh. con~act between ~aeh
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belt 18 and the respective opposed end faces of the rollsD
Shutters 22 are mounted within channels deined between
the opposed surfaces of the end walls 5 and plates 23
secured to the end walls and are movable vertically to
regulate the surface area of belt 18 in contact with the
powder within the hopper 4. Movement of the shutters is
effected by pegs 24 located in suitably shaped slots formed
in the plates ~3.
Figures 3a and 3b illustrate ~he shaping applied to
~he lower edges of each shielding plate 8 and each flexible
extension 7 of the hopper side wall 6 and Figures 3c to 3e
illustrate the po~sitions taken up by each shielding plate
8 with respect to its associated side wall 7 during,
respectively, start-up~ slow speed and normal operating
speed of the mill.
As will be seen from Figure 3a the lower margin of
the shielding plate 8 is shaped at its ends to provide
two downwardly protruding ears 25, the central length 26
of the margin being generally straight. The shaping is
~ symmetrical about the mid-point of the shielding plate
lower margin. From Figure 3b it will be seen that the
lower margin of the side wall 7 follows a straight line
normal to the side edges of the wall 70 In an alternative
arrangement, the lower margin of the shielding plate may
Eollow a concave curve over its entire lengthO
At start-up of the mill each shielding plate 8 is
positioned behind its associated side wall 6 so that
lengthwise-extending boundaries of the feed slot 9 of the
hopper are de~ined solely by the lower margins of the flexible
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extensions 7 of the hopper side walls. As the mi.ll
accelerates, the hopper 4 is raised to increase the flow
of powder to the roll gap; simultaneously each shielding
plate is lowered relative to the hopper so that its
depending ears 25 partially overlap the lower margi~ of
its associa~ed side wall extension. The protruding ears
25 shield the powaerapproaching the end zones of the roll
gap from the rolls 1,2 thereby offsetting the tendency of
~he edge bel~s 18 to draw powder i~to these end zones
thereby to main~ain the ra~es at which powder enters the
roll gap substantially uniform along its entire length~
When operating a~ the normal operating speed of the mill,
the ears 25 of the shielding plates 8 protrude completely
below the lower margins of the flexible extensions 7 so
that the lengthwise-extending boundaries of the feed 510t
9 are now defined by the lower edges of the shielding plates;
again, the fully protruding ears 25 restrict the flow of
i . : powder into the end zones of the roll gap to balance the
:; tendency o~ powder to be drawn into these end zones by the
20 . belts l8l Thus, at all speeds intermediate start-up and
normal running speed~ the ears 25 restrict the flow of
: powder to the end zones of the roll gap to enable normal
running speed to be achieved without high density bands
~ of powder appearing a~ the edges o~ the roll gap.
If~ as in conventional mills, the lengthwise~
extending boundaries of the hopper feed slot 9 were, at
all mill operatlng speeds, defined by shielding plates or
. . hopper side walls having straight lower edges similar to
. the side wall~ edge shown in~ Figure 3a, then the rate of
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feed of powder to the end zones of the roll gap 3 would
gradually increase with increasing mill speeds due to the
effect of the edge belts 18. In the embodiment described
above, it will be appreciated that the protruding ears 25
of the shielding plates 8 reduce the area oE roll surface
exposed to the powder exiting from the end regions of the
hopper feed slot 9, thereby restricting the rate at which
powder is fed by the rolls towards the end zones of the
roll gap. This restriction off-sets the feeding effect
which the edge belts have on the powder adiacent these
end zones,
In an alternative embodiment to ~hat illustrated in
Figures 1 to 3 3 the shielding plates 8 remain stationary
during aperation of the mill and the hopper 4 is raised
. and lowered relative to the shielding plates to vary the
configuration of the lengthwise-extending boundaries of
. the feed slot:9 in the manner set out above. In either
case, the shaping shown in Figure 3a~applied to the
: ; shielding plate may alternatively be applied to the lower
edges of the flexible extensions 7 of the hopper side walls
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In a further alternative unillustrated embodlment~
the ears 25 may be surfaced with a high friction materi.al
: (by suitable coating or treatment) to inhibit further the
flow of powder to the end zones of the roll gap. In this
embodiment, the ears 25 need not protrude to the same
: extent as they would if they were not so coated or treated
In the embodi.ment illustrated in Figur s 4a and 4b
each shielding plate assembly comprises a pair of side
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strips 27 which, in operation of the mill~ protrude below
the lower margin of the hopper side wall flexible
extensions 7. The end of the strips 27 and the ends of
the lower margin of the side wall extensions 7 are shaped
to provide a smooth transition at the slow-speed mill
operating position shown in Figure 4a and at the normal
operating position shown in Figure 4b.
In the arrangement illustrated in Figure 5 each
side wall extension 7 (or alternatively each shielding
plate) is surfaced at its lower outer edge with a high
friction material 28 such as emery cloth. The high
friction material restricts the flow of powder into
the end 70nes of the roll gap. In an alternative
construction the outer lower edges of the side walls of
the shielding plates may be roughened by a machining,
shot blasting or similar treatment.
Turning now to Figures 6a and 6b, each shutter
22 is formed on its surface facing the roll gap 3 with
a curved protrusion 29 which extends into the entry region
of the roll gap above the roll gap end zones to restrict
the flow of powder into these end zones. Movement of the
shutters towards and away from the roll gap 3 respectively
increases and decreases the restrictions imposed by the
` shutters on the rate at which powder flows to the end
zones of the roll gap, The~shutters 29 may be used in
combination with the shaped shielding plates~or hopper
side walls describedhereinbefore~ As will be seen from
Figure 6a the~base of the~shutter i6 shaped so that it
just clears the shielding~plates and roll6 when the shutter
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is at its lowest position and when the rolls are touching.
In a further embodiment of the invention, restriction
of thc rlow of particulate material to the end ~ones of ~he
roll gap is effected by suitable variation of the flow
properties of the material within the hopper. Thus~ a
suitable soli~ (eg. graphite), liquid (e g. oil or water)
or gaseous agent may be added to the powder in the hopper
differen~ially to vary i~s flow characteristics~
In each of the foregoing arrangements, it will
be appreoiated that the relative settings of the hopper~
the shielding plate assemblies and the edge belt shutters
are changed during changes of mill speed so as to con~rol
the flow of particulate material to the roll gap to maintain
the rate at which par~iculate material enters the roll gap
substantially uniform along its entire length. When
producing strip of a given thickness and density the total
mass of particulate material fed to the roll gap per unit
time will be increased as rolling sp~ed increases.
The shielding plates may be positioned behind their
~ 20 respective hopper wall~ instead of in front of these walls
; as previously described, Alternatively, the shielding
I plates may extend from behind through slots formed in the
hopper walls so that their lower portions lie in front of
thelower portions of the hopper walls.
25 ~ The relative~positions of the hopper, shlelding plate
assemblies and edge belt shutter may, for example, be
controlled as the mill accelerates and-de~a~celerates in
relation to the instantaneous values of roll speed by
reference to previously established empiri~al relationships
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for the particular type of strip being roll compacted.
Alternatively, their relative positions may be
controlled by providing control signals derived from
sensors which measure the thickness and density o~ the
roll compacted strip as it emerges from the mill. In
practice a series of such sensors, or one or more
scanning sensors could be used to provide information on
thickness and density across the full width of the strip~
These two methods may be used in combination by,
1() for example~ controlling the hopper~ shielding plate
assembly and edge belt shutter settings according to the
predetermined relationship with roll speed and making fine
~ adjustments from signals derived from the thickness and
; ~ density sensors.
It will be appreciated that other known methods of
control may be applied.
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